24TH ANNUAL
DWI
Available In Person, Livestream, & On-Demand At Your Own Pace For Up to a Year
P: 512.478.2514 • F: 512.469.9107 • www.tcdla.com • 6808 Hill Meadow Dr, Austin TX 78736
24TH ANNUAL TOP GUN DWI SEMINAR INFORMATION Date Location Course Directors Total CLE Hours
Friday, August 14, 2026 The Whitehall Hotel, 1700 Smith Street, Houston, TX 77002 Doug Murphy & Mark Thiessen 7.75 Ethics: 1.00
Friday, August 14, 2026
CLE: 7.75 Ethics: 1.00
Time 7:30 am
Topic Registration & Continental Breakfast
Speaker
8:15 am
Opening Remarks
Course Directors
8:30 am
0.75
Voir Dire: “One Question Voir Dire”
Neal Davis
9:15 am
0.25
TED Talk: Observations from First DWI Trial
Sean Evans
9:35 am
0.75
Defeating Drug Recognition Evidence with Scientific Studies
Doug Murphy
10:15 am
Break
10:30 am
0.75
Cross Examination: Top Ten Commandments
Ryan Gertz
11:15 am
0.75
Accident Reconstruction: What You Need to Know
Michael Reyes
12:00 pm
Lunch Buffet
12:15 pm
0.75
Lunch Presentation: Disconnect Defense: Winning Cases with High Breath & Blood Alleged Estimates
Mark Thiessen
1:00 pm
0.75
Examining Blood Discovery: Important Issue Spotting
Amanda Culbertson
1:45 pm
0.75
Winning Breath & Blood Cases without an Expert
Sean Darvishi
2:30 pm
Break
2:45 pm
0.50
Challenging Police Balance Arrest Tools (SFSTs) & Breath Testing
Chris McKinney
3:15 pm
0.75
Case Law Update: The Most Important DWI Cases for your Trial Notebook
Kyle Therrian
4:00 pm
1.00 Ethics
Zealously & Ethically Representing Clients: Lessons Learned From Over 50 Years of Practice
Rusty Hardin
5:00 pm
Adjourn
TCDLA :: 6808 Hill Meadow Dr :: Austin, Texas :: 512.478.2514 p :: 512.469.9107 f :: www.tcdla.com
Texas Criminal Defense Lawyers Association
24th Annual Top Gun DWI Table of Contents Friday, August 14, 2026 speakers topic
Neal Davis A One-Question Voir Dire? Sean Evans Simplify your DWI Trial Win The Ten Commandments of Cross Ryan Gertz Examination Accident Reconstruction and Injury Michael Reyes Biomechanics Sean Darvishi Defending Breath and Blood DWI Cases Chris McKinney DWI Judo
Criminal Defense Lawyers Project
24th Annual Top Gun August 14, 2026 The Whitehall Houston, TX
Topic: A One-Question Voir Dire?
Speaker:
Neal Davis Neal Davis Law Firm, PLLC 1545 Heights Blvd., Suite 700 Houston, TX 77008-4218 713.227.4444 phone 800.760.7140 fax neal@NealDavisLaw.com email http://www.houstoncriminaldefenselawyers.com/ website
6808 Hill Meadow Dr :: Austin, Texas :: 512.478.2514 p :: 512.469.9107 f :: www.tcdla.com
A One-Question Voir Dire? By Neal Davis (713) 818-3780 Neal@NealDavisLaw.com 1. Imagine a voir dire that comes down to one question. A Zen-easy voir dire. For you. For the panelists. Not a sales pitch. Not an argument. Not an attempt to change minds. Instead, envision a voir dire where you talk with the jury panel. Every single jury member (including those that end up not picked). You get to know them. You might even like them—and they might like you. And by the time the jury is impaneled, you know them far better than what they filled out on their generic jury forms. In short: a voir dire built around this one question that maximizes your odds of winning a case, no matter how hard the facts. Sound too good to be true? Ask Dick DeGuerin. A legal titan. Voted one of the Top 10 lawyers in Houston in the last 100 years. He’s tried more cases than anyone I know—and made a career out of winning the ones that were supposed to be losers. Recently, he used this one-question approach in a high-profile murder case involving a former sheriff’s deputy accused of shooting his wife three times. Another case most people thought was unwinnable. 48 Hours even covered it in January 2025.
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Once again, against the odds, the jury delivered the two sweetest words in the English language for a defense attorney.
Not guilty. Ask Grant Scheiner, an outstanding Houston lawyer, who has used this approach about a half-dozen times in sex-crime and domestic-violence cases, winning nearly all of them. Ask Coby Dubose, a younger Houston lawyer who has used this onequestion approach in his last 35 misdemeanor trials—some with brutal facts—and won every time. After one voir dire in a notoriously Statefriendly county, the prosecutor told him, flat out: “If your goal was to be a hell of a nice, likeable guy, then you did it.” Or ask me. I tried this approach and won six serious felony jury trials over the last 18 months (the seventh resulted in probation for a first-degree felony). Not a bad outcome. 2. This one-question approach applies to any type of case—civil or criminal, misdemeanor or felony. It just so happens that in today’s climate, with criminal justice reform and diversionary programs, the cases generally tried in Texas are violent crimes, sex crimes, certain intoxication offenses, and family violence cases. Rick Goldberg of Houston, Texas, is one of the country’s premier jury and trial psychologists. For more than three decades, he has worked thousands of cases—high-stakes civil defense, scorched-earth divorces, and complex criminal matters—quietly influencing outcomes long before most lawyers realize the ground has shifted beneath them. When Rick first saw the question, he did what the best trial lawyers do: he treated it as a hypothesis to be tested, not accepted on faith. In mock trials. In focus groups. In live courtrooms. Again and again. 2
He later told me: “This is the cleanest bias-extraction tool I’ve ever seen. Jurors don’t feel challenged. They don’t feel sold. They feel respected— and they tell you the truth.” Rick has used this approach in his own civil jury trials and, as of our last conversation, was undefeated—16–0 in jury trials, primarily in personal injury and insurance bad-faith cases, along with high-conflict divorces. To date, he has tested it in over 20 mock trials as part of a civil voir dire training module. Lawyers gravitate to it because it’s so simple. He insists his teams use it—not because it’s clever or novel, but because it works. It exposes resistance early. It eliminates guesswork. And it fundamentally alters the relationship between juror and lawyer. Rick put says: “That’s when I knew this wasn’t just a criminal-defense tool. It was something bigger—a way to let jurors tell you who they are before they ever get into the box.” To be clear: I’m not speaking hypothetically, theoretically, or metaphysically about an approach. We’re not interested in what might work. We care about what does work. It’s the scientific method. Hypothesis -> test -> result -> conclusion. This one-question voir dire was developed and tested in a few civil and dozens of criminal trials over more than two years. In cases of every kind (but mostly criminal). After asking me about it, Dick DeGuerin was the first to try it in trial, and he has continued to use it ever since. Judges almost never stop the question. A stray objection pops up now and then. It dies fast. Before voir dire, I give the judge a heads-up. One question. Every juror. One by one. The answer is almost always the same.
“It's your voir dire. I don't care. Do what you do.”
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Now I’ve gotten the green light. The judge has already decided he won't step in—even if it takes a little longer, even if the panel heads towards busted. Rarely the prosecutor tries to steal the question or blunt its impact by asking it first, but it hasn’t worked so far. By the time the prosecutor finishes the standard voir dire—the overview of the law, the Constitution, the watered-down explanation of reasonable doubt, the elements of the offense, the scaled questions, and punishment—there is little time left to use the question effectively. And the panel? They love it. After one voir dire, a venire member who never even made the jury tracked down the lawyer, who had used the question, on LinkedIn: "A
unique request here to connect, but I truly enjoyed the way you conducted voir dire. I saw we had some common connections and wanted to reach out. Take care!"
That's the point. People remember how you made them feel long after they've forgotten the legal instructions. I don’t know about you—but I’ve never had a panel member contact me after voir dire. Not once. Not to connect. And they’ve certainly never told me it was a positive experience. 3. What do the veteran lawyers—the old trial dogs—think of this new approach? Grant Scheiner: The ‘one-question’ format is dead simple and incredibly effective. It shifts the focus from short-term persuasion to identifying and eliminating venire members who are legally unqualified or psychologically resistant to the defense. A major bonus is how easily it exposes jury members who refuse to follow the law. Most strikes for cause become undisputed.
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Brent Mayr, a nationally-renown attorney on the faculty of Harvard Law School’s Trial Advocacy Workshop: In an intoxication manslaughter case, we had a huge panel of 110 jurors, but I got to ask the one question to each. It took about an about one hour. A veteran prosecutor came to watch. She told me afterward that she thought it was the best defense voir dire she had ever seen. The bailiffs came up to me after and said the same thing. The prosecutors told me that they went back to their office and told everyone the same thing. And leading East Texas criminal attorney Ryan Gertz: I have now used the one-question method in ten trials starting in November 2025. My experience with this method has been great. Before, I had been tinkering with various changes in my voir dire presentation trying to get better and more substantive responses from people. Inevitably, I was finding that 6-8 of the people who ended up on the jury had never said anything during voir dire and I knew almost nothing about them. That is an unsettling feeling. With One Big Question, I get to interact individually with each juror. This helps me get a sense of their personalities (outspoken v. introverted, etc.), how well they follow instructions, and when they have some reason they’re not a good fit or should be struck for cause. I love the implementation and execution of this method.
Calling it a one-question voir dire is a bit of a simplification. You ask other questions, of course, but this one question is the core one. You spend most of your time drilling down on it. Or, to use a different metaphor, the one question is the trunk of a tree. The other questions— about constitutional rights, defenses, and related issues in a criminal case—branch out from it. 5
Will you win every case? Well, if the case isn’t winnable, you probably won’t win it (and neither would Clarence Darrow). I lost a child sex abuse case because of devastating forensics and an incriminating statement. But the jury surprisingly recommended probation, far better than the State’s offer. Even when the rare conviction occurs, I have seen this approach often carry over into surprisingly good sentences. 4. Almost 30 years ago, I was a baby lawyer learning how to try cases. I was lucky to be in Texas, where courtroom giants like Joe Jamail and Racehorse Haynes were still walking the halls and arguing to juries in real time. Ted Poe was a criminal District Court judge at the time. He was a legend in his own right—a fierce former prosecutor, a serious judge who made everyone a better lawyer, and later a U.S. Congressman. One day I asked Judge Poe, “Who’s done the best voir dire you’ve ever seen?” He didn’t hesitate. “Mike Ramsey.” Mike Ramsey was a legal titan and co-counsel with Dick DeGuerin on the infamous Robert Durst murder case that ended in an acquittal. “Why?” I asked. Judge Poe said, “Because Mike would just talk to each juror individually on the panel—one-by-one—and by the end, he really knew who they were.” That stopped me cold. 6
I’d never heard of that approach. No lecturing. No selling. No looping panel members into persuading each other. No PowerPoints. No scaled questions. No dry recitation of the law. Just a friendly conversation, authentic and from the heart, punctuated by some Texas humor. What I didn’t understand then—it took me more than two decades to figure out—was that Mike Ramsey was making his defense points, building rapport, and establishing credibility. But most importantly he was smoking out bias—revealing potential jurors who were already inclined to vote against him. And it all came down to one question. I don’t recall exactly how he framed the question—he has since passed—but I had some idea. 5. Voir dire is our first—and only—real chance to talk with the people who will eventually be on your jury. After that, we talk to them: opening statements and closing arguments. No dialogue. No feedback. No correction. Voir dire is it. There is a reason it rivals cross-examination as the most important part of trial. A biased jury dooms the case before it begins, and a weak crossexamination leaves little hope of recovery. So why not squeeze every drop out of voir dire? How many lawyers leave voir dire feeling triumphant, only to learn— too late—that several jurors in the box never opened their mouths? Nothing. Not a syllable. Maybe they weren’t asked. Maybe they didn’t want to talk. Maybe they were nervous. Maybe they thought—wrongly—that staying quiet would keep them safe from being picked. 7
Those are the dangerous ones. The silent panel members. The ones who slip through untouched, untested, unknown. No one knows what they think or how they’ll vote. That’s not good strategy. That’s roulette. 6. Nearly 300 years ago, William Blackstone described voir dire—literally “to speak the truth”—as the mechanism for uncovering bias before jurors are impaneled. There are, of course, other goals, including: rapport, education, persuasion, humanizing the defendant, addressing weaknesses in the case, maybe rehabilitating some potential jurors. But those are secondary. If a potential juror in a murder case had a loved one murdered and cannot be neutral, who cares whether they like you, agree with constitutional rights in theory, or nod along when you explain selfdefense? 7. The best way to uncover bias is attorney questioning, not lecturing. And this process favors the defense. Absent meaningful attorney voir dire, the State enjoys a built-in advantage. Potential jurors tend to lean toward the prosecution for many reasons. Among them: institutional trust, assumptions of guilt (“he wouldn’t be here if he didn’t do something”), general views, or personal experiences with crime. Put 12 random people in the box, and odds are they’ll lean State. 8
That’s why courts that restrict attorney voir dire—federal court and some states—cripple the defense. The judge’s goal is speed: seat a jury, don’t bust the panel. The defense’s goal is removing every panel member who needs to be removed. Those goals collide. Judicial voir dire is safe and superficial. Without real questioning, bias stays hidden. And without exposing bias, you’re not selecting a jury. You’re gambling. With loaded dice. With someone else’s loaded dice. 8. I used to conduct an orthodox voir dire—honed over many years—and it worked well. An introduction of my client and me. An explanation of the importance of honesty—that a “good citizen” is someone who admits they cannot be neutral. A walk-through of constitutional rights. A review of the relevant law, including any defenses. Some case-specific or scaled questions. Then the usual fishing expedition for bias: “Who couldn’t be fair in a case like this?” And, finally, some rehabilitation of defensefriendly panel members. I’d thank potential jurors for their “candor,” even when it felt forced or absurd.
“Thank you, Juror Number Six, for calling my client a piece of crap. Really appreciate the honesty.” Yes, this really happened. No matter how sincere I tried to sound, it often came off as disingenuous—or worse, obsequious. At least I was not guilty of telling them, “I take by your silence that ….” And then, at the very end, I’d finally ask the one question. 9.
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I cannot recall the origin of this question—it probably was cobbled together from things I cribbed from different top lawyers. “Good artists copy, great artists steal.” So I’d ask the question. Briefly. Superficially. By then, everyone was exhausted. My time was almost out. And the judge was already mentally moving on to strikes. Everything felt rushed. I was getting answers—mostly perfunctory yeses and a rare no—from every potential juror. Yet I wasn’t really learning about them. In other words, I was asking the most important question of voir dire in exactly the wrong way. I did not know exactly what Judge Poe meant, or how Mike Ramsey did it, but I knew something wasn’t right. And worse, I saw no difference in outcomes using the question than not using it at all. 10. One day—sometime in 2023, as the COVID-era cases were finally coming to trial—my colleague Bill Stradley walked into my office. Bill is a great trial lawyer—plenty of chops, sincere in presentation, reasonable in tone. His father was a lawyer who worked closely with Joe Jamail, which is to say Bill came into the world with a genetic advantage. Bill said, “I’ve got a sexual-assault case coming up. What if, for voir dire, I take your last question—the one where you talk to every potential juror—and make it the whole thing?” He went on: “What if I tell them at the very beginning that this is the question I’m going to ask, so they should be thinking about it the entire time. Then I 10
cover the basics. And then I spend most of my time going juror by juror, talking through that one question for twenty or thirty seconds each?” That was it. That was the moment the one-question voir dire came to be—two roads meeting: the question I had formulated, and his instinct to make it the focus. We thought were onto something. But the jury—not us—would be the final judges. What we never expected was just how powerful it proved to be. 11. It’s time for voir dire. The jury panel has already heard from the judge. They know it’s a criminal case. Some may even know the allegations. A few grimaced when they heard them. They’ve seen everyone in the courtroom— including the defendant. A couple look at him with open disdain. The prosecutor has had the floor for an hour. The usual warm-up. Long, dull explanations of the law. Maybe some scaled questions. Some careful rehabilitation of State-leaning panel members flagged during the judge’s voir dire. The prosecutor gets a laugh or two with some canned jokes, but mostly the panel is polite, attentive—and bored. Then comes the break. Some rush to the bathroom. Others stretch or exchange pleasantries. Most reach for their cell phones. By the time you stand up, don’t you think the potential jurors already have a pretty good sense of the case? The allegations. The elements. The defenses. The constitutional issues. What they think of the prosecutor. What they think of the defendant, especially how he looks. On a conscious and unconscious level, the jury panel has already been exposed to a lot of information and is already forming opinions. 11
All of that—before you’ve said a single word. Now you’re up to bat. Imagine if you could ask them to return a verdict right now and tell you what they really think. In a way, that’s what you’re doing with this one question. You begin voir dire with an introduction:
My name is Neal Davis and I have the honor of representing Joe Smith in this very important case. All of us can agree with the State that child sex abuse is awful. But let’s be clear: that’s not why we’re here. We’re here because the State has accused Danny Defendant of this terrible crime and must prove it beyond a reasonable doubt. Then the windup:
There’s a saying that judges often tell jury panels: “Those jurors that walk,” meaning what a panelist says say often results in you being struck or excused. But those that don’t say anything? Well, they often end up on the jury. I want to do the best job I can for Danny Defendant. That means making sure that I’ve spoken with all of you who end up on the jury. One of my biggest fears is a jury of twelve of Danny Defendant’s peers, some of whom did not say a word. They’re on the jury and we don’t know the first thing about them. Then the tease:
So, I am going to discuss some legal principles and other things but before I do, I want to let you know that most of my time will be spent on one question. That question is: If you were me, should I want you on this jury?
This will be my last question. I want you to be thinking about it as we talk. In a moment, I’ll go one by one, from 1-65, in a row. I’m not going to jump around or catch you off guard. Everyone will get a chance to talk. No surprises. 12
Shoulders drop. A few people exhale. They’re relieved. They know what’s coming. The rules are clear. They can relax and listen. You’re not going to pick on them like the State did. You then touch briefly on the law: constitutional rights, the burden of proof—not guilty means not proven rather than innocent—and any defenses or issues unique to the case. You explain that you don’t expect sentencing to come up, but the law requires you to ask anyway—like wearing a seatbelt even when you don’t expect an accident. You rehabilitate where needed. Then you return to the one question that matters—the one you’ll spend the most time on. But before you ask it, you explain one more thing: Strong feelings.
Now I want to talk about that question I told you about at the beginning of voir dire. But before I do, I want to talk about strong feelings some people have. For example, a person might think: I have strong feelings that I could not be neutral in this kind of case because …. Here, you list your main concerns. In a child-sex case, I typically include: ◆ I am a victim ◆ Someone close to me has been a victim ◆ Too emotionally difficult for me ◆ I or someone close to me was falsely accused ◆ Kids don’t lie about something this serious ◆ The defendant looks guilty ◆ I work/volunteer with kids or have work/volunteer experience in this area And then, after you planted these seeds, you ask the big question (which you usually will follow up with smaller ones): 13
If you were me, should I want you on this jury? And then begin. You do exactly what you told them. You start with the first juror and go one by one, down each row, until the end. No skipping jurors, jumping around, trying to loop one juror’s answer into another’s, or asking if others agree. That might be tempting but defeats the purpose. Spend 20 to 30 seconds on each panel member, especially the ones that say NO. Ask them why not. Here you are laying the foundation for a strike—for cause or peremptory. Be in the moment, relaxed, spontaneous and completely open to answers (good or bad—they are a gift).
Q: So, Ms. Smith, you say NO. Why is that? A: Because [through tears] my younger sister was abused by our stepdad when we were kids. Q: I see that is very upsetting. It still really affects you decades later, doesn’t it? A; Yes [sniffling]. Q: Would you agree you wouldn’t be the best juror in this type of case? A; Yes. Q: Would you agree that you just couldn’t be neutral? A: I mean, I want to, but I just can’t. Q: You didn’t mention it earlier I guess when the prosecutor asked about anyone who had been a victim A: No, I just really didn’t think about my sister, only myself, and I hadn’t been.
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For panel members who say YES, avoid asking them why. At a minimum, you will educate the prosecutor; worse, you will develop a strike for cause for your opponent. Here’s how to do it:
Q: Ms. Johnson, you say YES. It looks like here you work as an assistant tech at Texas Children’s Hospital. That worries me, you know why? A: Yeah, um, because I’d believe anything a kid says. Q: Exactly, so you’re saying that’s not the case. A: Absolutely not. All I do there is sign kids in and out, and make sure they fill out a form, but I don’t really have contact with them. Most of my time is in the lab with the other techs. This is how NOT to do it:
Q: So, Mr. Brown, you say YES. Why is that? A: Because I was falsely accused by a student. I’m a teacher. Anyway, I got false accused and finally she admitted she lied but I lost my job …. The prosecutor would high-five you if he could. Sometimes, when I am genuinely interested in someone’s background or profession—which happens at least a few times with a panel—I will ask questions about that. The important thing is to be myself—everyone else is taken. I do not know of any better way to build rapport and a connection in voir dire:
Q: So, Ms. Williams, you say YES. It looks like here you own an art gallery. What type of art? A: Wow, I’m surprised you’d ask. Modern art. Q: Interesting, I went to art high school so I’m a big fan. Looks like your gallery is near Uptown Sushi. 15
A: Yes! Q: Love that place A: Me too! Where did you go to high school? Q: Houston High Arts, why? A: I had lots of friends who went there. What a small world …. Now we’re in sync. We know we share some common ground—maybe interests, maybe even mutual friends. We know the neighborhood. We like art. We agree on a good sushi place. And she likes what she’s heard so far and has, in effect, agreed to be a good juror. There’s almost always someone on the panel who hasn’t said much or has avoided answering the one question directly. For any number of reasons. They’re nervous. Disengaged. Or they think if they stay quiet, the lawyers will forget about them and they’ll skate. The fix is simple. Ask them: “What are your thoughts about what you’ve heard so far?”
Q: Ms. Rojas, you say “I don’t really know.” What do you mean by that? A: Ummm, I just don’t know. Q: Well, what are your thoughts about what you’ve heard so far? A: That he innocent. Q: What else? A. Sorry, my English not good. I can’t say anything. As these examples show, this question pulls out a goldmine of information you would almost never get any other way. I mentioned this to David Berg, whose works on trial advocacy I had admired, and he said: “You have managed to synthesize into one valuable question the lesson I 16
learned in 1979—let the panelists talk. Or, as it is written in the Bible: ‘You don't learn shit with your mouth open.’” Ms. Rojas, for example, had never been asked—and was too embarrassed to volunteer—that English wasn’t her first language until the question was put to her directly. The panel that included Ms. Smith was asked about sexual abuse in general, but she said nothing. It wasn’t until the question was asked of her, individually, that she finally spoke up. And then there’s the harder call: the panel member who insists they can be fair despite everything you’ve just heard. The sexual-assault panel member who, through tears, says she can be fair in a sexual-assault case. The detective with decades in law enforcement who thinks he can be fair—or wants to believe he can. You can’t fault them. No one wants to think of themselves as biased. But you know better. Throughout voir dire, you’re constantly taking in information—how panel members look, how they sit, their tone, their pauses, their body language, their temperament, their confidence, their education. And you’re picking up far more unconsciously than consciously. As the saying goes: “More is caught than taught.” Trust that. Your instincts are usually right—especially when it comes to what a panel member really believes, even when they can’t admit it to themselves. 12. When you rise for opening, the jury isn’t a mystery anymore. You’ve talked to every panel member. You know them as well as anyone can under the circumstances, and you used that knowledge in striking the jury. Unlike the usual dry, forgettable prosecutor, you’ve built a genuine 17
connection. They know you. They trust you—because you were real. You’re not a salesman or a cardboard cutout or someone to doubt. You’re a three-dimensional human being—and at least some kind of like you. As you rise, the woman with the art gallery looks relaxed and offers a small smile. The Texas Children’s Hospital tech assistant is locked in— living up to her promise to be fair, not reflexively believe a child’s word. Now, you’re not guessing. Now, you have your best chance to win.
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Criminal Defense Lawyers Project
24th Annual Top Gun August 14, 2026 The Whitehall Houston, TX
Topic: Simplify your DWI Trial Win Speaker:
Sean Evans Thiessen Law Firm 733 E 12 1/2 St. Houston, TX 77008 832.247.1083 phone sean@thetexastrialattorney.com email
6808 Hill Meadow Dr :: Austin, Texas :: 512.478.2514 p :: 512.469.9107 f :: www.tcdla.com
Simplify your DWI Trial Win: Cross Examination and The Texas Exclusionary Rule
Introduction The goal of this paper is to illustrate one strategic method of handling a DWI jury trial. This method is not a one-size-fits-all defense for every DWI case, but simply an alternative approach to consider. This method is particularly useful in misdemeanor cases, and when the facts of your case, or the court you are in, make it unlikely for you to win suppression motions with the judge. Filing pretrial suppression motions and arguing those motions before trial (or after jury selection) often results in evidence still coming into trial. This alerts the state and their witnesses to your plan of attack to their case, and if you have cross-examined a witness, that witness now gets a second chance at answering your questions in front of a jury. This time, with better answers, and a more polished delivery of their testimony. The strategy suggested by this paper is to effectively use cross-examination to raise fact issues about the lawfulness of police conduct in obtaining evidence in your case. Then, using a 38.23 Jury Instruction, implore the jury to disregard any evidence “it believes” was obtained in violation of the law. Instead of a hearing outside the presence of the jury, require the witness to answer your questions for the first time, live, in front of the jury. The jury needs to hear the witness “err”, “umm”, and “I don’t know”, hear when you draw out critical admissions for your case, and see the witness off-balance and unable to answer your basic questions with honesty. These moments are powerful, memorable, and what sticks in the mind of jurors in deliberations. Doing a pretrial suppression motion that is likely to fail, dilutes the power of these moments and destroys your tactical advantage of surprise. I.
The Federal Exclusionary Rule
The “exclusionary rule” originated in early Supreme Court cases challenging the admissibility of evidence obtained in violation of the Fourth Amendment of the U.S Constitution. It is a judicial rule created by the Supreme Court, that gives “teeth” to the Fourth Amendment by allowing judges to exclude evidence collected in violation of the Fourth Amendment. Without this rule, the Fourth Amendment is just a prohibition on police conduct without a remedy. The exclusionary rule was eventually applied to the states in Mapp v. Ohio, and in Terry v. Ohio the Court held that the exclusionary rule was the only way to enforce Fourth Amendment violations. Mapp v. Ohio 367 U.S 643 (1961). Terry v. Ohio, 392 U.S. 1 (1968).
Since then, the Supreme Court has carved out certain exceptions to this rule, like the “good faith” exception created in United States v. Leon 468 Us. 897 (1984). Also see the inevitable discovery exception in Nix v. Williams, 467 U.S. 431 (1981). The Court has also sought to limit the application of the rule, or to exclude evidence only when there is intentional or flagrant disregard for the Fourth Amendment. Herring v. United States 555 U.S 135 (2009). (In Herring, a recordkeeping mistake by an individual maintaining a warrant database did not justify applying the exclusionary rule to exclude evidence). This is because the behavior of law enforcement must be sufficiently deliberate to trigger the possibility of “meaningful deterrence”. More simply put, law enforcement should fear exclusion of evidence if they knowingly or intentionally violated the Fourth Amendment in obtaining it. These exceptions and limitations come from the Supreme Court’s current focus on deterrence. Minor mistakes, or Fourth Amendment violations that lack “deliberateness” will not result in the application of the rule at the federal level. II.
The Texas Exclusionary Rule
Texas has codified its own version of this rule in Tex. Code Crim. Proc. Art. 38.23: “(a) No evidence obtained by an officer or other person in violation of any provisions of the Constitution or laws of the State of Texas, or of the Constitution or laws of the United States of America, shall be admitted in evidence against the accused on the trial of any criminal case. In any case where the legal evidence raises an issue hereunder, the jury shall be instructed that if it believes, or has a reasonable doubt, that the evidence was obtained in violation of the provisions of this Article, then and in such event, the jury shall disregard any such evidence so obtained. (b) It is an exception to the provisions of Subsection (a) of this Article that the evidence was obtained by a law enforcement officer acting in objective good faith reliance upon a warrant issued by a neutral magistrate based on probable cause.” The Texas rule offers broader protection to a defendant than the federal rule and has far less exceptions and limitations than its federal counterpart. 38.23(b) has codified one singular exception to the rule: “when evidence is obtained by a law enforcement officer acting in objective good faith reliance upon a warrant issued by a neutral magistrate based on probable cause”. Because DWI arrests are almost made exclusively without a warrant, prosecutors cannot use this exception to neutralize a defendant’s challenge to the admission of evidence.
The First Court of Appeals has explicitly DECLINED to extend the Texas good faith exception to an officer’s reliance on a statute, if evidence was still obtained unlawfully. State v. Tercero, 467 S. W. 3d 1 (Tex. App.—Houston [1st Dist.] 2015. In State v. Daugherty, the Court of Criminal Appeals confirmed that the “inevitable discovery” exception recognized by the federal rule DOES NOT apply in Texas. State v. Daugherty, 931 S. W. 2d 268 (Tex. Crim. App. 1996). The court’s reasoning is based on the rules of statutory construction. The legislature specifically included this singular, limited version of the good faith exception as the ONLY exception in the statute. “Where a statute contains an express exception, it’s terms must apply in all cases not excepted. 67 Tex.Jur.3d Statutes Sec 120. “In construing a statute, it is not ordinarily permissible to imply an exception… nor may an exception be engrafted on a statute by implication merely because there seem to be good reason for doing so. 67 Tex.Jur3d Statutes Sec 121.” (Id.) Standing is still required to make the exclusionary rule challenge. Unlike the federal rule, which is limited to constitutional violations, the Texas rule allows defendants to challenge evidence collected in violation of ANY federal or state law. This covers a wide range of law enforcement actions for a defendant to challenge, but is not all-encompassing. This ability to challenge evidence obtained in violation of seemingly ANY law, has been qualified some in Chavez v. State. In that case, the Court of Criminal Appeals held that the violation of law complained about must be one that directly invades the Defendant’s rights. An officer may break the law independently while collecting evidence, but that law violation must invade the privacy or relate to the rights of the defendant for the rule to apply. Chavez v. State, 9 S. W. 3d 817 (Tex. Crim. App. 2000) For example, an officer violating multiple traffic laws to initiate a traffic stop based on reasonable suspicion, and then seizing evidence based on probable cause, will not result in exclusion because the law violations were not those that affected defendant’s rights. A defendant will NOT have standing to invoke the exclusionary rule, when evidence is obtained through a violation of ANOTHER person’s constitutional or statutory rights, such as evidence found in the arrest of a third person, or a co-defendant’s confession. Windom v. State, 379 S.W.3d 463, 469-70 (Tex.App.—Beaumont 2012, no pet). Neal v. State, 256 S.W.3d 264, 284 (Tex.Crim.App. 2008). In Thomas v. State, the Fourteenth Court of appeals in Houston made an important distinction related to standing. That court held that state and federal constitutions apply only to law enforcement officers, so if a defendant wants to exclude evidence obtained by a
civilian third party, she must show it was obtained in violation of some law. Thomas v. State 586 S. W. 3d 413 (Tex. Crim. App.—Houston [14th Dist.] 2017). In Thomas the court held that information obtained in violation of a “breach of computer security” statute by a private citizen would trigger exclusionary rule protection. III.
Independent Source Doctrine
While there is no other exception to the rule, Texas has adopted the “independent source doctrine” used at the federal level. It is not an exception to the rule, but rather describes a situation when evidence found through a source independent of the “tainted search”. This evidence is not obtained “in violation” of the law and therefore will be admissible. Wehrenberg v. State, 416 S. W. 3d 458 (Tex. Crim. App. 2013). IV.
38.23 Jury Instructions
A defense attorney can use 38.23(a) in three different ways to challenge evidence: 1) Filing a pretrial Motion to Suppress; 2) Objecting to the admissibility of evidence at the time it is offered; (3) OR, through cross examination, dispute or challenge the State’s version of the facts which they rely on to establish the legality of the arrest. Bell v. State, Tex.App— Houston [14th Dist.] 1994, pet. Ref’d. The defendant may, but is not required to, object to admission of evidence as well as requires jury instruction. Holmes v. State, 248 S.W.3d 194, 202 (Tex.Crim.App. 2008). To receive a 38.23(a) jury instruction to disregard evidence a defendant must have standing, and must meet three other requirements: 1) Must raise an issue of fact; 2) The evidence of that fact must be affirmatively disputed; AND 3) The disputed factual issue must be material to the lawfulness of the conduct that resulted in obtaining the challenged evidence. Hamal v. State, 390 S.W.3d 302, 306, 308 (Tex.Crim.App. 2012); Robinson v. State, 377 S.W.3d 712, 719-20, 722 (Tex.Crim.App. 2012); Madden v. State, 242 S.W.3d 504, 510 (Tex.Crim.App. 2007). 1. Raising a Fact Issue An issue of fact is raised by presenting evidence, from any source, whether strong, weak, contradicted, unimpeached, or unbelievable, that controverts the State’s evidence of the material facts of an arrest, detention, search, or seizure. Garza v. State, 126 S.W.3d 79, 85 (Tex. Crim. App. 2004). Upon proper request, the defendant then has a statutory right to receive this jury instruction. If the relevant facts are uncontroverted, then the lawfulness of the acquisition of evidence is a question of law for the trial court, and the defendant is not entitled to an instruction. For example, in Doyle v. State, the defendant was stopped for weaving into
oncoming traffic, and the defendant admitted that he was weaving. The defendant’s excuse or reason for weaving did not entitle him to instruction because the fact that he was weaving was undisputed. Doyle v. State, 265 S.W.3d 28, 33-34 (Tex.App.—Houston [1st Dist.] 2008, pet. Ref’d). 2. Facts Must be Affirmatively Disputed There must be affirmative evidence that puts a fact in dispute. The mere possibility that a jury may not believe a witness does not create a factual dispute triggering the statutory requirement for an instruction. Only ANSWERS on cross examination, not questions, may affirmatively dispute facts. Madden at 513-14; Cadoree v. State, 331 S.W.3d 514, 521 (Tex.App.—Houston [14th Dist.] 2011, pet. Ref’d). 3. Fact Issue Must be Material The disputed fact issue must be material to your claim of a law violation that, if resolved in your favor, would render the evidence inadmissible. Hamal at 306, 308). For example, the fact issue of whether a defendant was parked illegally was held immaterial, when a license plate violation created probable cause for the arrest. Spence v. State, 325 S.W.3d 646, 654 (Tex.Crim.App. 2010). Similarly, a dispute about the precise location of seizure of evidence was held immaterial because evidence was found in the search of the “premises” described in the warrant. Jones v. State, 338 S.W.3d 725, 740 (Tex.App.—Hosuton [1st Dist.] 2011, on reh’g.) Your 38.23 instruction must be set up in trial through cross examination or presentation of evidence, and argued in this, way if it is to survive an objection from the state on including it in the charge. There is also another, easier, way, to get the charge included without dealing with any of this procedure: by agreement with the state, or at least with no objection. In misdemeanor DWI trials, I don’t spend a lot of time and effort haggling over the charge to the jury. Instead, I use that as an opportunity to find some agreement with the state on other parts of the charge. In exchange, they are typically willing to include what I want for my client’s case: a 38.23 instruction to the jury that tracks the language of the statute. I have received more resistance to this in felony cases, where the state is more likely to object to this instruction if you did not affirmatively dispute material facts. Ensuring this jury instruction is included in the charge, works in conjunction with proper voir dire, and your overall cross examination strategy to increase your odds of success with the jury. This is especially true when you are working without your own expert witness.
V.
Using 38.23 Effectively
The most powerful part of this provision for DWI attorneys defending their clients in a jury trial, is the second half of 38.23(a) regarding jury instructions: “In any case where the legal evidence raises an issue hereunder, the jury shall be instructed that if it believes, or has a reasonable doubt, that the evidence was obtained in violation of the provisions of this Article, then and in such event, the jury shall disregard any such evidence so obtained.” When bringing this around in closing arguments to the jury, you always phrase this as “if you believe that evidence was obtained in violation of the law, then you SHALL disregard it”. Let the state or judge correct you on this. (They probably won’t, given the fact it’s an “or” provision). The phrase “If it believes”, in the context of sufficiency of evidence, has a clear connotation of being less proof than “has reasonable doubt”. Just considering the plain language of the two phrases, “if it believes” has no qualifier of “reasonableness” on it. In a way it’s like saying “some doubt” or “a doubt’, is sufficient, rather than “a reasonable doubt”. We WANT jurors latching onto their beliefs or gut feelings that evidence was obtained in violation of the law. If they believe it, then they SHALL disregard it (or so our argument goes). If we conduct voir dire properly, we intentionally frame the jury’s understanding of this issue through deliberate use of language and hypotheticals to the entire panel. We then effectively raise fact issues during trial about the lawfulness of the evidence obtained. In closing arguments, we remind the jury they each agreed to disregard evidence they believe was obtained in violation of the law, and that a proper verdict requires that they SHALL disregard any such evidence. There are numerous Texas statutes that can be violated by officers during a DWI investigation that might result in evidence being obtained unlawfully. You must cross-examine each witness with the objective of raising the possibility of law violations. Doing this effectively and convincingly will require the jury to disregard evidence, even if the judge allowed it in.
Criminal Defense Lawyers Project
24th Annual Top Gun August 14, 2026 The Whitehall Houston, TX
Topic: The Ten Commandments of Cross Examination Speaker:
Ryan Gertz Gertz Law 2630 Liberty St Beaumont, TX 77702-1914 409.833.6400 phone 409.833.6401 fax rgertz@gertzlawyers.com email
6808 Hill Meadow Dr :: Austin, Texas :: 512.478.2514 p :: 512.469.9107 f :: www.tcdla.com
The Ten Commandments of Cross Examination – A Practical Guide for Texas Criminal Defense Lawyers Ryan Gertz of the Gertz Kelley Law Firm Board Certified in Criminal Law: Texas Board of Legal Specialization and the National Board of Trial Advocacy
Introduction Cross examination remains one of the most powerful weapons in a criminal defense lawyer’s arsenal. In criminal trials, where the stakes are often life or liberty, a well-executed cross examination can dismantle the State’s case, expose holes in their hypotheses, and plant seeds of doubt for closing argument. But, when executed poorly, destruction follows and citizens accused often accompany the bailiff from the courtroom. This paper and presentation expand upon the classic framework developed by Judge Irving Younger — the “Ten Commandments of Cross Examination” — with practical insights tailored to modern Texas practice. Further, it incorporates the work of Larry Pozner and Roger Dodd, who have written the definitive treatise on Cross Examination. Whether you are defending a DWI, a sexual assault, or a complex white-collar case, these principles, when adapted to the specifics of your case and your skill-set, provide a reliable roadmap for effective advocacy. The Commandments focus, primarily, on destructive cross examination. That is the type of cross examination where you want to convince a jury not to believe or lend credence to a witness proffered by the government. Alternatively, you can use them for the purpose of turning a state’s expert witness into your expert witness. But, do so with caution. Trying to go head to head with
an expert requires substantial knowledge of the subject matter and the ability to pronounce and define complex terms correctly. One slip up here can backfire entirely. Also, the Commandments are not rigid dogma but battle-tested guidelines. They reward preparation, discipline, and strategic restraint — qualities every Texas defender must cultivate. And, you have to practice. Learning the Commandments is valuable, but the only way to master the craft is to employ them over and over again; every trial, every time. After a while, they will become second nature and you will start to see real benefits.
The Ten Commandments First Commandment: Be brief, be short “Cross examination is a commando raid, not the invasion of Normandy,” Judge Younger says. Keep it short, focused, and memorable. Juries appreciate efficiency; they resent lawyers who waste their time. And, if they don’t like you, they won’t hold out for you or your client when the going gets tough in deliberations. Moreover, so many people’s attention spans have diminished, due to television and social media, that you must make your points quickly and sit down in order to command their attention. Aim for impact in under ten minutes when possible. Less is more. And, your brevity signals confidence. Think of the points you want to make with a witness and how they will impact your summation. My father, who was a litigator for fifty years, and believed in Abraham Lincoln’s lawyering style, loved to cite Lincoln: “if the government has five things they must prove to win their case, do not bicker over each of them. Pick their weakest link and focus in on that, concede
the rest.” This should dictate the points you want to make on cross. If your case is about intoxication, focus the government’s witnesses on what they didn’t do right or could have done, but neglected to, in order to prove intoxication. Did they administer the SFSTs correctly? Did they employ good science on the breath or blood test? Did they really do a thorough investigation into your client’s intoxication? If your case is about causation, then concede intoxication and focus on who caused the accident and all the things they did not do or investigate regarding causation. Pozner and Dodd would describe those points as a chapter in a book (see The Eighth Commandment). As efficiently as possible, make the witness concede the points you want to make and then close that chapter and move to the next. Younger would say, though: “Never make more than three points; two better than three, and one best of all.” While this may not always be practical in complex litigation, make it a goal. Practical Tip for Texas Practice: In counties with crowded dockets and limited jury trials, judges reward concise examinations. Save your energy for the witnesses who truly matter. Perhaps even question: “should I cross examine this witness at all?” Sometimes, the best cross examination is standing up and saying: “I have no questions for this witness.” You signal to the jury that the witness was so worthless that you are not going to waste your time or theirs trying to impeach them. Second Commandment: Use Plain Words and Short Questions Speak the language of the jury, not the law library. Lawyers (and cops, doctors, and engineers) tend to want to show how smart they are by using big words. Justice Scalia once suggested, when arguing to Judges, “sacrifice everything on the alter of clarity.” For jurors, this is
even more true. Using words they don’t understand, or are not part of their everyday speech, only serves as a distraction. There’s a children’s book series called Fancy Nancy where a girl named Nancy teaches kids fancy words, like: “parfait is a fancy word for sundae.” Lawyers in trial want to do this same thing. For example, I was trying a case once and somehow used the word “ostensibly” to describe the complainant’s timeline of events. The Judge chided me jokingly, while the jury was deliberating, that several jurors probably thought it had something to do with Austin, TX and keeping it weird. What’s worse, after I made the mistake, the prosecutor doubled down on it and used that word twice in closing argument. Think of words we use in court and purposefully make replacements. Replace “operate the motor vehicle” with “drove the car.” Replace “alcoholic beverage” with beer or wine or whiskey. Replace “altercation” with “fight.” But, don’t let the State replace “intoxication” with “impairment.” Aside from simple words, short, simple questions reduce confusion and help you maintain control of a witness. Long, compound questions invite objections and evasion. Additionally, avoid questions with subjective or vague words. For example, don’t ask the State’s expert: “there’s a big difference between .08 and .17, don’t you think?” This question violates several Commandments at once, but here, “big difference” and “don’t you think” invite answers you will not like. A witty expert is going to point out that those BACs both qualify as intoxication or they might fight you on what is a “big difference,” or they may just start spouting some opinion that you didn’t expect because you asked “don’t you think” at the end of your question.
Third Commandment: Use Only Leading Questions Leading questions are your primary weapon on cross. The Rules of Evidence specifically permit leading questions on cross examination and forbid them on direct examination and you must take advantage of this fact. Tex. R. Evid. 611(c). The purpose of cross examination is for you to put words in the witness’s mouth and they need to be your words. Judge Younger would say: “the melody of a cross examination should be sung by the lawyer; with an occasional monosyllabic response from the witness.” According to the Book of Matthew, Jesus said something to the effect of “wide is the path that leads to destruction.” Questions that begin with “who, what, when, where, how, why, or explain,” are that path. You will be so tempted to use them on cross. Don’t. Leading questions allow you to testify through the witness. Non-leading questions allow the witness to make a speech or say anything they want. Worse still, you cannot control their answers nor object to them, because you’re the one that asked the open-ended question. Related to this topic is the question: what really constitutes a question? If you are leading the witness with short questions and only adding one fact per question, the State may get up and object that you’re not really asking the witness questions. This is probably true if you are doing it right. Some lawyers use a trigger at the end of each question to signal to the witness that it’s a question, for example, “correct” or “isn’t that right?” But, after a while this becomes a crutch or a distraction. In an effort to avoid that, skip it altogether or try putting some at the beginning of the question like: “wouldn’t you agree” or “I’d be correct if I told this jury…”. Usually an objection about your questions on cross not really being questions just means you’re kicking ass and the State (and sometimes the prosecutor in the robe on the bench) want to get you off kilter. When that
happens, ask the next two or three questions with the triggers and then go back to making statements that the witness must agree with. Make the State object again and the jury will get it before long. You’re killing their witness with facts and they’re whining to the Judge about it. Practical Tip for Texas Practice: One of the intro words that seems to create confusion for Judges and lawyers as to whether a question is leading or not is the word “did” at the beginning of the question. For example, you might ask what you think is a leading question: “Did you interview anyone else at the scene?” The Officer may respond with: “Yes. I spoke with Bob Smith and he said….” Now, you have a problem: your question wasn’t really leading and invited more of an answer than you were anticipating and now is going to require a hearsay objection about what Bob told the Officer. However, if you used the word “didn’t,” the outcome would be different. “You didn’t interview anyone else at the scene?” should only trigger a “no” or a “as a matter of fact I did” type of answer allowing you to maintain control over the witness and what comes next. And, the “as a matter of fact I did” answer leads directly into the next Commandment. Fourth Commandment: Never Ask a Question to Which You Do Not Know the Answer This is the golden rule. Cross examination is not a deposition and it is not the time to conduct discovery. Frankly, if you are following the Commandments above, you will not often violate this one. But, you mustn’t. While it is easy to say and hard to do, preparation is everything—review all reports, statements, body cam footage, 911 calls, and prior testimony. In Texas, the Michael Morton Act helps with this, but, verify everything yourself.
Usually, though, preparation is not where the Fourth Commandment bites you. It is the unexpected person or observation in the Courtroom (that there is no way to prepare for) that invites you to violate the Commandment. For me, it was a twenty-five year old girl with a spaghetti strapped shirt and purple streaks in her hair. I was trying an intoxication manslaughter punishment case (pled guilty went to jury for punishment). The “girl” was the mother of a five year old boy she had with the decedent, though they were not together any more. The government asked her if thirty years in prison was enough punishment for my client killing her son’s father and seriously injuring another person. She replied that: “thirty years can’t be enough. How do you put time on a life? Prison is not enough for the person who took my son’s father away.” Well, after looking at her, gauging her age, her outfit, and her hair, I decided to probe her experience on cross examination despite not knowing anything about her. The questions and answers went something like this: Q:
You told the jury thirty years in prison was not serious enough for this offense.
What do you know about prison? A:
I used to work at the prison.
(This was the first clue that I had stepped in a bear trap. And, it was not a leading question, so I’m violating multiple Commandments at once. But, I made it worse.) Q:
Well, tell the jury, tell them what prison is like.
A:
They have recreation, art classes, shop classes, gym time, and they are able to walk
around the campus freely. It’s basically like a high school for adults. (Now, I am dying. I have violated multiple Commandments, multiple times and I am on an island.)
Q:
Were you at a maximum security facility?
(Again, I have no idea what the answer is and I am not leading the witness, I am simply fishing for a life line. Thankfully, she gave it to me.) A:
No, I worked at a prison exit facility.
(I should have sat down here, but I didn’t.) Q:
So, that’s different than the kind of facility [my client] would end up in if the jury
sent him to prison for causing the death in this case? A:
Well, the prison classification process is complicated and, since he has no criminal
history, he could end up in a low security unit like the one I described. (So, now I am violating multiple Commandments, over and over again). I finally managed to unfurl myself from this disaster and, remarkably my client got eight years from the jury for the manslaughter with no deadly weapon finding and probation for the assault. But, my cross examination of that witness was NOT the reason for that result. The case was tried in front of my good friend Judge Larry Gist, a fifty year jurist and a big proponent of the Ten Commandments who is now deceased. We would have dinner or drinks routinely and, for the rest of his life, he would occasionally sit next to me and whisper: “what do you know about prison?” That will teach you not to violate the Fourth Commandment. Exception (rare): When the answer cannot hurt you no matter what the answer and you need to lock in a fact for summation. Put differently, a lot of the preliminary questions to law enforcement, for example, you don’t know for certain how they’re going to answer, but you don’t care what the answer is because it helps you either way. For example: “Officer, you agree with me that a DWI investigation must be thorough?” Well, you don’t know this officer’s answer, but it won’t hurt if
he says “yes” and it will help even more if he says “no.” Or, this one that you don’t know the answer to: “Officer, if given the choice of my client driving home drunk or sleeping it off in the parking lot of the restaurant, which one is safer in your mind?” Obviously, there are ways that could go awry, but the officer may come off looking stupid if he answers incorrectly. Fifth Commandment: Listen to the Witness’s Answers Hear what is actually said, not what you expect. Follow up on helpful slips. If a witness volunteers something damaging to the State, pause, let it breathe, then move on or lock it in. Texas juries notice when you are alert and responsive. When a witness says something untenable, illogical, irrational, or just dumb, don’t fight with him about it. Just sit down and let the bad answer ride. If you fight with him or continue probing it, he may realize the mistake and try to correct or explain it. Years ago, I tried a case three times (two hung juries and a lesser conviction for attempted murder) involving my client shooting at two plain-clothes Sherriff’s Deputies. My client was running away from them and fired a shot over his shoulder. A bumbling and disoriented crime scene investigator had been put in charge of the scene and the diagrams and evidence gathering. He had drawn a not-to-scale, rudimentary diagram of the scene and noted that a window behind where the deputies were had a bullet hole in it that was about four feet off the ground. Since he hadn’t measured the scene, I asked him if the hole in the window was a significant distance from where the deputies would have been standing and he agreed it was, but then volunteered that it was “like 200 yards.” Well, we had made a diagram of the apartment grounds and this was an absurd estimate. It would have been more likely 100 – 130 feet (much more in the range of the distance of a pistol fired directly at deputies rather than over their heads as a warning). So, after hearing that answer I closed that chapter and let the
absurdity of his answer be a key problem with their case, not just in the first trial, but in the second and third as well. Clearly, a projectile from a pistol would not maintain a four foot height for two hundred yards if fired directly at the deputies and we used that fact with the State’s ballistics expert and the lead investigator to our advantage. This principle is true with answers to you on Cross Examination, but also true as to their answers on Direct Examination. In June, I tried a double sexual assault of a child case (two different complainants). My client, prior to hiring me, went to the police station and gave an interview. He seemed forth coming in his denials that anything had taken place with his younger nephew. But, at some point the Detective asked him if the boy had every touched him and he responded: “as far as I know, no.” The State and the Detective went on and on about this being evidence of deceit or a Freudian slip indicating that the boy had touched him. Later, during testimony from the Child Advocacy Center director, the last question the State asked was: “that was the only interaction you’ve had with this young man?” The witness answered: “as far as I know, yes.” Now, if you’re not listening to the witnesses’ answers this might pass you by. Instead, I chose to take advantage of the contrast: Q:
A moment ago, you qualified your last answer by responding: “as far as I know.”
A:
Yes, I did.
Q:
I expect it was not your intention to be dishonest with this jury by doing that.
A:
No, it certainly was not.
Q:
In fact, wouldn’t you agree that you added that qualifier in an effort to be truthful?
A:
Yes, I see lots of kids, and I did not want to commit if I wasn’t sure. I may have seen him at the grocery store or something, I don’t know.
Q:
But, it was not an effort by you to be dishonest or undermine your answer.
A:
No, it was not.
In closing, we were able to point out that people often use that phrase in an effort to be honest, rather than dishonest. Fortunately, the jury believed my client rather than the complainants and acquitted him. 6. Exercise Control Over the Witness and Yourself This Commandment is really several concepts wrapped into one: don’t quarrel with the witness, don’t allow the witness to repeat the things said on direct examination, don’t allow the witness to explain his/her answer to your questions, and don’t bargain with the witness. Judge Younger stated this as: “Don’t quarrel with a witness!” My father would express it differently. He would routinely say: “Never get mad at a witness unless the jury is mad at the witness.” When a witness is not answering or is clearly lying about something, it is easy to get frustrated with that witness. Often your frustration as the lawyer, though, looks like arrogance to the jury. Control yourself and keep your same tone and pace. The more the witness avoids answering simple, fact driven questions, the more biased or untruthful they look. And, never argue with a hostile witness on the stand. You will lose credibility with the jury. Stay calm, professional, and in control. If the witness is hostile, use short, leading questions to box them in. Save your argument for closing.
Part of exercising control over a witness is to not give him/her an opportunity to reinforce or clarify things testified to in direct examination. And yet, as Judge Younger points out, many lawyers on cross examination begin with the phrase: “Sir, I would like to clear some things up,” and then ask a series of questions reinforcing the points the witness and the State were making on direct examination. If you believe “clearing things up” for the jury is something you are supposed to be doing as defense counsel, you misunderstand your role in this process. As with every good rule, there is an exception. If the government has an expert on the stand, and they have noticeably omitted relevant or exculpatory evidence, then you can cross examine about that evidence to “clear things up.” But, that does not mean re-establishing the points made on direct examination. Another challenge that commonly arises during cross examination is a request by a witness to explain his/her answer to your questions. If you are asking short, leading, one fact per question questions, the witness likely will feel the need to explain something that is hurting the State’s case. That simply means you are being effective in your cross examination. You cannot allow a witness to get out from under your thumb by letting the witness explain their answer. Instead, depending on the context, I usually reply with one of the following responses: “I am sure the prosecutor explained this to you, but, this is a question and answer exercise. I ask the questions and your job is to answer them truthfully. Can you do that?” “I understand that you’d like to explain your answer, but Mr. Prosecutor that called you to the stand can give you the opportunity to explain yourself. During my examination, you are required to answer the questions I ask you. Do you understand?”
Or, simply: “No, the State may let you explain, but your answer to my question was sufficient.” Now, some Judges and/or prosecutors may try to interject and try to encourage the witness to expound. If this keeps happening, you may want to reconsider whether your questions meet the first four Commandments. Often you will find, your question was complicated, ambiguous, or included imprecise adjectives. But, if your question is: “the sky was clear that day” and you are getting pushback from the witness, the State, or the Court, you need to hold firm. Finally, under the heading of controlling yourself, do not bargain with the witness. I hate seeing young lawyers start their cross examination with some soliloquy like: “I am going to make you a deal. I am going to ask straightforward questions that call for a ‘yes’ or ‘no’ answer and I would like you to answer them that way.” Kill me now. If you are following the first four commandments, you likely won’t need this. But, worse still, what if the government objects or the court calls you down for not allowing the witness to tell the whole truth. Not a great way to start off an effective examination and control the witness. On that same note, though, when a witness is being non-responsive or evasive, do not try to bargain with him/her and do not go to the court for help. Instead, reevaluate your question(s). Is it leading? Is it short and to the point? Are you adding too many facts or using too many adjectives? If you feel the need to bargain with the witness you are not controlling them, yourself, or the room. It’s your cross examination. It’s your court room. Use the Commandments and control it.
7. Add One Fact Per Question Larry Pozner and Roger Dodd, two very experience litigators, maintain that the best manner to achieve witness control and control of the courtroom is to ask only one new fact per question. Have you ever heard a lawyer (or yourself) ask a question like this: “You saw the sixfoot, five-inch, 225 pound guy with the bloody fists beat down the five-foot, seven-inch boy with the bloody face?” There are a lot of facts packed into that question and its problematic for multiple reasons. First, if the facts matter to your case, packing them all into one question makes them less likely to be fully understood by the jury in one fell swoop. Second, though, if you’re off on one fact, you’re inviting the witness to quibble with you about that one fact and the entire point will be lost. Instead, do this: •
You saw the fight
•
John was fighting
•
John is six feet five inches
•
John weighs more than 200 pounds
•
John was fighting Dave
•
Dave is five-feet, seven inches
•
John is a taller person
•
John weighs more
•
John hit Dave
•
With his fists
•
John’s fists were bloody
•
You saw blood on Dave’s face
•
You saw John beating Dave
•
With his fists
•
In his face
Here, each question adds one relevant fact. And, if you can get the witness to agree with each of your questions because they are simple and fact driven, after a while, the witness will be unable to disagree with you about anything. Each question should contain no more than one new fact. But, you can loop or compound facts that the witness has already agreed to. This commandment really covers several key concepts. First, even though it may seem more efficient to ask the one, big, multi-fact question, the reality is that the jury will digest these facts better if fed to them one at a time. Secondly, though, it’s important to understand the concept of sponsorship for the jury. In essence, a jury will put more stock in facts, admissions, or concessions made by a witness the State has sponsored than one you have called to the stand. So, each morsel that you extract from a witness on cross examination is much more palatable than those provided by your client or some witness you sponsor. Using this method stretches out, but actually simplifies the facts that are important to your case while allowing those facts to come from the State (in essence) rather than your interested or hired witness. One of the best things to be able to do in closing argument is point out a damaging fact to the jury and then say: “I am not telling you that, Mr. [state’s witness] told you that.” This method allows you to do that most effectively and memorably. 8. Use the Chapter Method Pozner and Dodd also espouse a concept called the Chapter Method for cross examination. A chapter is simply part of the story that you want to tell or a point you intend to make in summation. As you have studied the facts of the case, the statute, and the indictment, you should know what the weakest links in the State’s chain are. You want to develop clear chapters.
The title of the chapter is sign posting for our brain. It’s like the heading of an outline. Some lawyers feel the need to write out every question in advance, but if you are using the Chapter Method effectively, the title of the chapter ought to dictate for you how the questions go. The disaster scenario in writing out all of your questions in advance is being inflexibly stuck to those questions. For example, you ask: “it was a clear day?” and the witness says: “yes, and hot and dry.” Now, if the next two questions for your chapter logically would have been “it was hot” and “it was dry,” the witness has already stated that, so, listening to the answer you close the chapter on the conditions and move on. But, if you are enslaved to your prepared questions and not listening to the answer you will do this a lot less nimbly. Be prepared to cut a chapter short if you get the answer that makes the point of that chapter. The chapter heading can serve as a mental sign post to you, but, sign posting is important for the jury, too. When moving from one topic to another on cross examination, tell the jury where you are going. “Now, I’d like to turn your attention to the field sobriety tests you administered to my client.” Post with caution, though. You can become argumentative with sign posts “now, I’d like to turn your attention to the roadside agility tests you improperly administered to Mr. Smith,” may seem fun, but is likely going to draw an objection from the DA and a rebuke from the Judge. Let those argumentative points become clear through your examination, rather than through your sign post. 9. Do Not Ask the One Question Too Many In his original presentations of the Ten Commandments, Judge Younger would humorously admit that there are not really ten commandments, only six or seven. But, he thought ten had a
literary ring to it and so some of them overlap. In this revised version, that is true for Commandments Nine and Ten, BUT, they are phrased differently to teach different things. Know when to stop. This is a skill that drinkers and cross examiners both struggle with. It seems to be going so well and you’re having so much fun. But, if you don’t stop when you need to, you will make a mess of everything. Another way to phrase this is: “Don’t ask the ‘one question too many.’” The challenge is, you usually don’t know that you’ve asked it until the witness begins answering and you have lost control. And, one way to catch your self if to consider your inner monologue and stop yourself when your next question is about to begin with “So,….” Typically, starting a question with that word means you are about to ask the witness to agree with some premise or argument that is not based on simply one new fact, but rather something you want the jury to know. For example, imagine this exchange: Q: We agree then that Mr. Smith demonstrated one out of eight clues on the walk and turn test? A: Yes. Q: And we agree that he swayed while performing the one leg stand, but did not demonstrate any other clues? A: That’s correct. Q: You’ve also admitted that you did not correctly administer the HGN test, because you only administered ten passes instead of fourteen? A: Unfortunately, yes. What should you do now? SIT DOWN. And, argue in closing that all of the signs of intoxication the officer is trained to find from this book filled with tests, he did not find in your
client that night. But, your inner monologue is demanding that you ask one more question to make it super clear for the jury: “So, he didn’t demonstrate the types of clues of intoxication that your training and experience would require to make an arrest?” Lovely question, until the answer is: “well, he had the distinct odor of alcohol on his breath and person, his driving showed multiple indicators of intoxication from the NHTSA manual, and as you know, intoxicated people with high tolerance may be able to perform well on the SFSTs because they are younger or more agile than others.” And, now your carefully crafted cross examination is lost. Thinking of the Chapter Method above, clearly establish in your mind what your chapters are for that particular witness. Only ask the questions you must in order to complete that chapter and then sit down. Put differently, once you have scored your points, STOP. The “one question too many” often rescues a witness or opens the door to harmful evidence. End on a high note. Conclude when you have made your most valuable point. Do not be forced into sitting down when the witness has issued you a right hook. The jury will notice. 10. Save the Ultimate Point for Summation You should start every case doing the following tasks in this order: 1) Read the indictment, 2) review the relevant statutes in the Penal Code for that indictment and make sure the Government has met all the elements and properly pled their case, 3) review the discovery, and 4) begin thinking about your closing argument based on the first three tasks. But, here is the thing: you are never going to get a government witness to agree to the key points you want to make in closing. Instead, you should take advantage of a jury’s curiosity. Ask leading questions, adding one fact per question, and then stop when you get to the edge.
Do not ask any witness to agree with the premise of your entire case. Plant the facts during cross examination and argue their significance in closing. Jurors expect you to connect the dots in final argument. Again, if you find yourself saying the word “so,” STOP! That’s the indicator that you are about to try to get the witness to agree with a premise of your closing argument (and it’s also likely a one-question too many) and they never will. Worse still, they will probably use it as an opportunity to give some big long answer that hurts your case. The best time to do this arises when you have one great, perfect, amazing piece of evidence - that breaks the whole case open - and the State does not know about it. These times are rare, really rare, but you have to watch for them in every trial. When you have that rare occasion arise, you have to resist the temptation to explain it to the jury or have a witness say what it means. Instead, save it for summation. As an example, last year, we were trying an injury to a child case. The State’s position was that shaking was the mechanism of the infant’s head injuries. And, of course, my client, Austin, was the sole suspect, as he was the last one holding the infant. Fortunately, when Austin arrived home from work at 5:09 p.m., he found his wife, the baby, and his wife’s pre-teen sister all sleeping on the couch and took a photo of his wife and baby. It was a cute picture. A few minutes later, the wife and sister left to go to softball practice and Austin was left with the baby. Thirty minutes later, the baby was catatonic and he rushed the baby to the hospital. From there, the baby was sent to Texas Children’s who diagnosed her with abusive head trauma, the mechanism: shaking. So that’s how it is pled in the indictment. Upon careful inspection of the photo of the baby, from the day of the incident and only moments after Austin returned from work, the baby had a large knot and bruise on the front right
portion of her forehead. During cross-examination of the mother, we entered the picture of them from that day into evidence through her. We didn’t discuss it with her, show it to the jury, or ask any of the doctors who testified about it. We saved it for summation. It’s so tempting to do otherwise, but you have to resist the temptation. Showing the bruising to the jury, after multiple doctors have testified it must have been shaking that caused the injuries, not a short fall or a drop, is like putting a bomb in the jury box and it has the desired impact. Save it for summation.
Conclusion Mastering these Ten Commandments will not make every cross-examination a home run, but it will dramatically improve your batting average. Preparation, discipline, and strategic restraint separate good defenders from great ones. In the high-stakes world of criminal defense, your crossexamination may be the difference between conviction and acquittal. Practice these principles in every case. Record your trials (where permitted) and review them critically. Share techniques with colleagues. The craft improves through deliberate repetition. The defense of liberty depends on skilled cross-examination. Go forth and command the witness stand.
Additional Trial Skills Considerations •
Impeachment Tools: Master Texas Rules of Evidence 609 (prior convictions), 613 (prior inconsistent statements), and 615 (production of statements). Always have extrinsic evidence ready. Always begin impeachment of a witness the same way, so they know they have stepped in the trap. The best impeachment opening line is: “have you ever testified differently,” or “have you ever said/written something different than that?”
•
Expert Witnesses: Cross experts with learned treatises (TRE 803(18)) and clear, simple hypotheticals. Make sure you can pronounce the words you use with experts (encephalopathy, candida albicans, pathognomonic, etc).
•
Law Enforcement Witnesses: Focus on training, policies, deviations from protocol, and body cam gaps. First, build up their credibility and get them to agree they must be thorough, detail oriented, and open-minded in their investigations and report writing. Phrases like “That’s not in your report, is it?” or “you never spoke with that witness,” are powerful in undermining that credibility. And, purchase and study the books they are trained with, or should be. Get to know the NHTSA Manual, the Breath Test Operator’s Training Manual, and key treatises about the topics of your big cases (murder, sexual assault, psychology, etc.) You can learn a lot about what they know and don’t know by getting well versed in those types of manuals and books.
•
Cultural Awareness: Texas juries vary widely—urban, rural, conservative, diverse. Tailor tone and examples accordingly without sacrificing professionalism. Dress like yourself (and your clients should too). If you do not normally wear cowboy boots and a hat, don’t wear one to a courtroom in Jasper or Midland.
•
Ethics and Decorum: Maintain respect for the court and witnesses. Zealous advocacy does not mean rudeness. If the jury does not like you, they will vote against your client.
Endnotes / Suggested Reading •
Irving Younger, The Ten Commandments of Cross-Examination (video lecture)
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Pozner and Dodd, Cross Examination: Science and Techniques
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Klonoff and Colby, Winning Jury Trials: Trial Tactics and Sponsorship Strategies
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Texas Rules of Evidence
Criminal Defense Lawyers Project
24th Annual Top Gun August 14, 2026 The Whitehall Houston, TX
Topic: Accident Reconstruction and Injury Biomechanics Speaker:
Michael Reyes J Eftekhar & Associates 20689 IH 10 West San Antonio, TX 78257 210.313.0820 phone mreyesjea@gmail.com email
6808 Hill Meadow Dr :: Austin, Texas :: 512.478.2514 p :: 512.469.9107 f :: www.tcdla.com
J. Eftekhar & Associates Michael Reyes, Ph.D., BME, C.E.O TCDLA August Presentation Accident Reconstruction and Injury Biomechanics Methods and Techniques and Their Application in Criminal Defense Cases. I.
Introduction
This paper presents the discipline of Injury Biomechanics and its relationship with Accident Reconstruction. Both experts evaluate crashes, however, each expert answers completely different questions. The Accident Reconstructionist evaluates how a crash occurred by applying engineering principles to the analysis and evaluation of physical evidence, vehicle data, and scene information. The Biomechanics Expert evaluates how the injuries happened by applying principles of biomechanics, anatomy, and physiology to the evaluation of occupant kinematics and documented injuries. The Biomechanics Expert typically relies on the findings and opinions of the Accident Reconstructionist but will in turn confirm that its findings and opinions are consistent with those of the accident reconstruction. It is rare for the methods of either one of these disciplines alone to be dispositive. Rather, they are more often informed by each other and yield mutually supportive conclusions. Having knowledge of the applicable methods and techniques, when they should be used, and in what manner allows a criminal defense attorney to triangulate the evidence, thereby aiding in mounting the most credible defense and effectively discrediting the Prosecution’s case. The engagement of an expert is fundamentally a question of return on investment: Do the nature of the charges and the attendant consequences of a conviction justify the expenditures entailed when hiring an expert to assist in securing an acquittal, a reduction in sentence, or the complete dismal of charges? It is the aim of this paper to provide a knowledge base to assist in answering this question. II.
The Haddon Matrix and Human-Vehicle-Environment Triangle1
Mental frameworks are useful in methodically assessing the relationships between factors and evidence that contribute to the events of a crash and the resulting injuries. Two of these are the Hadon Matrix and the Human-Vehicle-Environment2 triangle. The Haddon Matrix
In addition to vehicle crashes, both paradigms possess utility in the analysis of other incidents (e.g. pedestrian and bicyclist cases). 2 HVE (https://edccorp.com/index.php/hve-software) is an industry-standard suite used by forensic engineers, researchers, and law enforcement (via HVE-CSI). It uses physics programs like EDCRASH (kinematics/crush energy) and EDSMAC (simulation of trajectories and impact forces) to calculate initial speeds, delta-V (change in velocity), and post-impact spin-outs. 1
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J. Eftekhar & Associates Michael Reyes, Ph.D., BME, C.E.O TCDLA August Presentation (Table 1) aids in establishing the factors and phases (pre-impact, impact, post-impact) which make up a collision. The HVE triangle ( Figure 1) serves as a reminder of the two-way relationships between these three factors, where any one factor has a relationship with the other two. The goal of these paradigms is to triangulate the evidence from any one of the H-V-E factors to the other two. The reader is encouraged to view the remaining material with these frameworks in mind. Factors →
Human
Vehicle
Environment
Driver skills
Maintenance of brakes, tires, Roadway condition and steering Lighting condition Collision mitigation systems Weather condition
Phases ↓ Pre-event
Driver attentiveness Sobriety Pre-existing conditions Event
Human tolerances to crash forces
Traffic control devices Vehicle crashworthiness
Roadway geometry
Airbag deployment
Roadside objections
Restraint use
Terrain type and topology
Designs to minimize likelihood of post-crash fire
Gouges and scratches
Restraint use Post-event Crash victim’s health status Medical care (both on- and off-scene)
Tire marks Vehicle recovery Impacted objects
Table 1: The Haddon Matrix for (https://www.safetylit.org/haddon.htm)
Motor
Vehicle
Occupant
Safety
Human
Vehicle
Environment
Figure 1: Human-Vehicle-Environment triangle.
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J. Eftekhar & Associates Michael Reyes, Ph.D., BME, C.E.O TCDLA August Presentation
III.
Triangulation of Evidence
One of the tasks of the reconstructionist and the biomechanics expert is to match each piece of evidence from one of the H-V-E factors to the other two. For example, the location, direction, and length of pre-impact skid marks on the roadway (Environment) in conjunction with the trackwidth of a car and its tread pattern (Vehicle) identify which vehicle produced the skid marks and how it was positioned on the road when it was braking. Another example would be matching an occupant’s injury pattern (Human) with an interior windshield strike (Vehicle). The benefits of this process are that it places increasing constraints on the resulting analysis, thereby allowing for the development of the most plausible incident scenario. The story ultimately presented to the jury should be like a strand of DNA (
Figure 2). Because each amino acid of DNA links only with a specific partner, a gap in the DNA can be recreated; i.e. the information encoded by a strand of DNA is based on mutually supporting pieces (the amino acid pairs). In contrast, the story told by connected links of a chain falls apart if any link is broken.
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J. Eftekhar & Associates Michael Reyes, Ph.D., BME, C.E.O TCDLA August Presentation
Figure 2: The story told to the jury should be like a strand of DNA composed of mutually supportive pieces. A story which is like a chain falls apart if any link is broken.
IV.
Sources of Information
The information that both the accident reconstructionist and biomedical expert rely on may be gathered by the State or developed by the Defense’s retained expert. In Texas, the documentation typically takes the form of a Texas Peace Officer Crash Report or a Major Crash Packet. The Texas Peace Officer’s Crash Report includes information related to the date and time of the crash, the crash location, the involved individuals and vehicles, and the environmental conditions. The Crash Report also includes Contributing Factors, an Investigator’s Narrative Opinion of What Happened, and a Field Diagram. The information contained in the Crash Report is a documentation of basic facts of the case (e.g. location, individuals, vehicles) and description of the collision sequence. The Crash Report also includes qualitative information (e.g. vehicle damage rating) or opinions (e.g. an occupant’s seating position or restraint use) which, to be well-founded, may require a higher level of expertise than is possessed by the reporting officer. A Major Crash Investigation is conducted by the Texas Highway Patrol Division in crashes involving a fatality, serious injury, or complex, highly destructive collisions. This investigation is conducted by DPS officers or Crime Scene Investigation personnel with training specifically aimed at collecting data of a more quantitative nature which requires a higher level of technical knowledge to document and interpret. The documentation is referred to as the Major Crash Packet, and may include: • • • • • •
Texas Peace Officer’s Crash Report Dashcam and/or Bodycam video Ground-based crash scene photographs Drone aerial photographs of the crash scene 3-dimensional point cloud data (e.g. Faro scans) and models Scaled scene diagrams 4|Page
J. Eftekhar & Associates Michael Reyes, Ph.D., BME, C.E.O TCDLA August Presentation • • • • • • • • • •
Major Crash Investigation Report or Inter-Office Memorandum Major Incident Notification Vehicle inspection reports Vehicle Event Data Recorder files (dashcam video and vehicle telemetry) Witness statements Skid tests Speed calculations Medical Examiner’s / Autopsy Report Autopsy photographs Toxicology Report
Depending on the scope, nature, and quality of information, the Major Crash Investigation may be sufficient for the Defense’s biomechanics expert to render the needed opinions, thereby eliminating the need to retain an Accident Reconstructionist. If it is not, then an Accident Reconstructionist will be needed to address gaps in the State’s documentation and methodology. In any case, it is often useful to retain an accident reconstructionist as early as possible to evaluate the data to at least determine if the available information is sufficient for a reconstruction. If additional evidence must be gathered, it is imperative that this be done as quickly as possible due to the evidence’s transient nature (e.g tire marks disappear, vehicles are scrapped with the loss of valuable ACM data, and biological evidence degrades). In the event the scene has changed over time, photographs, body-cam and dash-cam videos, and laser scans are often the most beneficial sources of data. Photogrammetry techniques can be applied to these to establish the location of physical evidence. In cases where significant time has elapsed and physical evidence has disappeared or been destroyed, these may be the only evidence documentation available. V.
Accident Reconstruction Aim
The aim of the accident reconstructionist is to describe, in as much detail as possible, the events of a collision. For each vehicle involved, this requires determining particulars such as: • • • • • • •
Position on the road Heading Direction of travel Speed Acceleration and deceleration Rotation Impact severity (Delta-V and PDOF) 5|Page
J. Eftekhar & Associates Michael Reyes, Ph.D., BME, C.E.O TCDLA August Presentation
The reconstructionist typically determines these details for a particular time and place during the three-phases of a collision sequence (pre-impact, impact, post-impact). It is imperative that the reconstruction quantify each factor, as opposed to loose, qualitive descriptions. The goal is to base the analyses on sound methodologies so that the findings and opinions are robust and can withstand cross-examination. Scene Data Scene data is useful to both the accident reconstructionist, and the biomechanics expert as a means of describing the interactions of the vehicles and people with the environment. For the accident reconstructionist, physical evidence on the roadway can be used in conjunction with vehicle data (e.g. researched specifications, technical vehicle inspections) to establish the positions and dynamics of a given vehicle on and off the road during the three-phases of the crash sequence (pre-impact, impact, and post-impact). For the biomechanics expert, the scene data is part of the evidence which allows the reconstructionist to perform the analysis needed for determining such things as occupant kinematics, ejection trajectories, and pedestrian throw distances. For the accident reconstructionist, key pieces of scene evidence related to the vehicle and its dynamics include: • • • • • • • • • • • • • •
Skid marks Yaw marks Acceleration scuffs Flat tire scuffs Roadway friction (skid tests) Imprints Road scars and scratches Material transfers or deposition (e.g. paint transfer and chips) Debris fields and location Fluid stains Trip location (where a rollover initiated) Impact locations (between vehicles, with roadside objects, and with the surface during a rollover) Launch and landing location (in vaults) Vehicle final rest location
Key pieces of scene evidence related to a person (vehicle occupant, pedestrian, or bicyclist) include:
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J. Eftekhar & Associates Michael Reyes, Ph.D., BME, C.E.O TCDLA August Presentation • • • • • •
Scuff marks from footwear (both on- and off-road) Footwear imprints (off-road surfaces) Material transfer from clothing and personal items Biological (blood, hair, tissue) material transfer Location of personal items Final rest position of person
The above evidence aids the biomechanics expert in establishing the initial contact location between an ejected occupant (fully or partially) or struck pedestrian with a surface or object, the post-contact movement path, and the person’s final rest position and posture. It is important to note that scene-evidence created by a person is subtle, transient, and may be overlooked or misinterpreted during the State’s investigation. Vehicle data (exterior and interior vehicle inspections, ACM and ECM imaging, VEDR video and telemetry) Data obtained from vehicle inspections is used by the accident reconstructionist and/or biomechanics expert to assess how the vehicle interacted with other vehicles, the environment, and the people involved in the incident. At the scene of the collision, the State will typically gather information to identify the make, model, and year of the vehicle, perform a basic assessment of the damage in the form of a damage rating3, and assess occupant restraint use. In fatality cases, technical procedures are employed to gather evidence. As the State’s investigators could commit errors in evidence gathering, interpretation, and analysis the utility of this information must not be taken at face-value and should be assessed by the Defense’s retained experts. A technical vehicle inspection is the primary source of data utilized by the accident reconstructionist and biomechanics expert. The documentation typically takes the form of photographs, laser scans, direct measurements, imaging of a vehicle’s Airbag Control Module (ACM) or Engine Control Module (ECM), and downloading of data from Video Event Data Recorders. For the accident reconstructionist, key pieces of evidence establishing interactions between vehicles, and vehicle and the environment (scene) include: •
Contact and Induced damage4
Prior to 2026, a vehicle damage rating was given an alphanumeric descriptor of the form XX-ABC-Y, where XX is the Direction of Force (1 – 12 o’clock), ABC is the Damage Description (2 or 3 letter code), and Y is the Damage Severity (0-7). Starting in 2026, the alphanumeric descriptor was changed to a written description consisting of Vehicle Damage Direction of Force, Vehicle Damage Description, and Vehicle Damage Severity. Example: 12-FD-3 indicates a 12 o’clock direction of force, with the impact distributed across the front end of the vehicle, and exhibiting a damage severity of 3 out of 7. 4 Contact damage: Deformation or defacement resulting from direct pressure of another object or surface in an impact; direct damage. 3
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J. Eftekhar & Associates Michael Reyes, Ph.D., BME, C.E.O TCDLA August Presentation • • • • • • • • •
Imprints Rub-off Material transfer Scratches, gouges, and abrasions Crush extent and direction Condition of tires, brakes, steering, lighting, and signals ACM and ECM data VEDR data GPS vehicle trackers
For the biomechanics expert, key pieces of evidence to establish the crash severity (important to determine survivability) and the interactions between the vehicle and the occupant include: • • • • • • • •
Degree of occupant compartment intrusion (quantified as crush) Witness marks (e.g. interior windshield strikes, damage to interior surfaces and components) Biological evidence deposition (including DNA evidence) Location and degree of occupant compartment intrusion Restraint and airbag-specific witnessmarks Seat positions Seat damage Passenger vehicle ACM data
An airbag control module (Figure 3) is designed to work with sensors to detect a crash pulse, make a Non-deployment / Deployment decision, have sufficient reserve power to deploy airbags, and record pre-crash vehicle status. Note that the primary function of the ACM is to make the Deploy / Non-Deploy decision and, in a Deployment Event, deploy the airbags and fire the seatbelt pretensioners. The recording of any additional information is an ancillary function.
Induced damage: Damage to a vehicle other than contact damage. Often indicated by crumpling, distortion, bending, and breaking. Induced damage includes damage done by another part of the same vehicle. Definitions taken from Traffic Crash Reconstruction, 2nd Edition published by Northwestern University Center for Public Safety.
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Figure 3: Examples of airbag control modules. The ACM: May be referred to by other abbreviations depending on the manufacturer. For example: • •
RCM (Restraint Control Module): Ford, Lincoln, Mercury SDM (Sensing and Diagnostic Module): General Motors brands, including Chevrolet, Buick, GMC, and Cadillac • ORC (Occupant Restraint Controller): Chrysler, Dodge, Jeep, and Ram • SAS (Sophisticated Airbag Sensor): Mazda A Crash Data Retrieval (CDR) kit is used to image the ACM (Figure 4). A successful data retrieval results in the production of several files which include a raw .cdrx file, a PDF Report, and an Excel file. It is common in criminal cases for the State to only produce the PDF report. PDF files can be manipulated, so it is important to push for the production of the raw .cdrx file. From an evidentiary point of view, the .cdrx file is the best evidence as this file cannot be manipulated and can be re-interpreted by successive versions of the CDR software. Further, the State often retains the ACM as evidence. This presents an opportunity for the Defense’s accident reconstructionist to re-image the module using the latest software.
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Figure 4: Steps in the imaging of an ACM leading to the production of a CDR report (https://cdr.boschdiagnostics.com). Crash data parameters are presented (in tabular or graphical form; Figure 5 - Figure 6). ACM data useful to the accident reconstructionist includes: • • • • • • •
Indicated vehicle speed Brake status Steering wheel angle Engine throttle Accelerator pedal position Transmission gear position Crash Severity (Delta-V from which PDOF can be calculated)
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Figure 5: Example of pre-crash data imaged from an ACM and presented in the CDR Report.
Figure 6: Example of crash pulse data imaged from an ACM and presented in the CDR Report. 11 | P a g e
J. Eftekhar & Associates Michael Reyes, Ph.D., BME, C.E.O TCDLA August Presentation ACM data useful to the biomechanics expert includes: • • • •
Restraint use Occupant seat sensor data Seat position indication Crash Severity (Delta-V from which PDOF can be calculated)
Occupant restraint use can be determined using information contained in the CDR report that is generated when the vehicle’s ACM is imaged. The indication of restraint use or nonuse must always be checked against the physical evidence of interior contacts and the occupant injury pattern. Restraint use is explicitly indicated for the front row outboard seats: System Status at Deployment: • Driver's Belt Switch Status: Buckled • Passenger's Belt Switch Status: Unbuckled Pre-Crash Data (-1 sec): • Safety Belt Status, Driver: Buckled • Safety Belt Status, Right Front Passenger: Unfastened (Off) If the occupant’s size and weight are known, the seat position and occupant size classification information provided by the CDR report can useful in establishing where an occupant was seated. For example, the seat position parameter may indicate that the driver’s seat was positioned in a manner incompatible with who is claimed to be the driver (a Rearward position when the “driver” is short in stature) or a front passenger Occupancy status which is incompatible with weight of the individual who is claimed to have been in that seat. In many vehicles, the passenger seat track position and size classifications are recorded alongside the driver's seat settings (Figure 7). • • • •
Driver Seat Position Switch: Rearward Occupancy Status, Passenger: Adult (AM50) Buckle Switch, Left Seat: Buckled Buckle Switch, Right Seat: Buckled
For American domestic and various other vehicles, the exact fore/aft position of the seat track is monitored to calibrate the frontal airbag module. •
Configured for Driver Seat Track Position Sensor: Yes 12 | P a g e
J. Eftekhar & Associates Michael Reyes, Ph.D., BME, C.E.O TCDLA August Presentation • • •
Driver Seat Track Position Switch Circuit Status: Rearward Passenger Seat Position Switch Circuit Status: Rearward Automatic Passenger SIR Suppression System Status: Air Bag Not Suppressed
How to Understand the Data: •
Foremost / Yes: Indicates the seat is pushed all the way forward (within designated manufacturer thresholds). This usually results in a lower-force deployment to protect the driver/passenger from sitting too close to an inflating airbag.
•
Rearward / No: Indicates the seat is slid back, away from the closest proximity to the airbag.
Figure 7: Example of pre-crash data indicating Belt Status and Occupant Size Classification. An Engine Control Module (ECM) is the central computer for a semi-truck’s engine (Figure 8). Core functions include engine management, emissions control, speed limiting, and system protection. The recorded data is typically presented in tabular and graphical form and includes: • • • • •
Vehicle speed Throttle application Brake application Cruise control status Engine RPM
An event is recorded by the ECM (Figure 9) when the system deceleration threshold (typically 7 to 9 mph decrease over one second) is met or exceeded, as may occur in hard braking. As 13 | P a g e
J. Eftekhar & Associates Michael Reyes, Ph.D., BME, C.E.O TCDLA August Presentation the ECM event recording is not triggered by a crash pulse, the event data must be correlated to the date and time of the crash and the recorded data assessed for consistency with the known facts of the case. The ECM may be referred to by other abbreviations: • • •
ECU: Electronic Control Unit PCM: Powertrain Control Module EDC: Electronic Diesel Control
Figure 8: Example of heavy vehicle ECM module mounted to engine.
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Figure 9: Example of ECM Sudden Deceleration data. 15 | P a g e
J. Eftekhar & Associates Michael Reyes, Ph.D., BME, C.E.O TCDLA August Presentation A Video Event Data Recorder (VEDR) is an onboard device that captures both visual footage and vehicle telemetry data during a crash. VEDR data are useful in determining the actions of the driver, vehicles, and pedestrians involved in an incident. The system typically has an outboard facing camera (looking towards the roadway) and an inboard camera (looking towards the driver). A VEDR integrates multiple data streams into a single timeline for crash reconstruction. The recording of video and data by the VEDR relies on an event trigger (e.g. crash deceleration, hard braking, hard cornering) which isolates a segment of data bracketing the trigger time. Typically, 10 to 30 seconds of data and video footage are captured which may span the entirety of the crash sequence, or only portions. Data recorded by the system includes: • • • •
Vehicle Speed Longitudinal and lateral accelerations Brake Status Outboard and inboard video
Figure 10: Example of a Lytx VEDR system and inboard and outboard facing video (https://www.lytx.com/vedr-service-providers). 16 | P a g e
J. Eftekhar & Associates Michael Reyes, Ph.D., BME, C.E.O TCDLA August Presentation VI.
Biomechanics
Injury biomechanics is the science that examines how mechanical forces, accelerations, and energy transfer during a crash act upon the human body to cause physical trauma. It bridges engineering and medicine to explain exactly how and why tissues, bones, and organs deform or fail under impact loads. An injury analysis typically follows the following steps: 1. Define the Injury. 2. Quantify the vehicle dynamics and impact severity (e.g. Delta-V and PDOF). 3. Determine the occupant kinetics and kinematics within the vehicle. 4. Determine if the mechanisms of injury necessary to produce the reported injuries were present in the subject collision. Data
Source
Comprehensive description (injury type, location, & severity) of injuries of all vehicle occupants, pedestrians, or bicyclists
Accident vehicles Medical records & diagnostic imaging Witness / occupant statements and depositions
Forensic data confirming occupant contact and location with the environment, vehicle, and other occupants
Accident Vehicles Accident Scene Witness / occupant statements and depositions
Human tolerance data
Experimental data on human tolerance (whole body, structure, organ / tissue) Studies injury and survivability studies based on staged and real-world collisions.
Restraint system: characteristics
use
and
functional
Accident vehicles Injury pattern Witness / occupant statements and depositions
Vehicle kinematics and kinetics (PDOF and Delta-V for all significant motions)
Accident vehicles Accident scene Numerical calculations Witness / occupant statements and depositions
Table 2: Data and sources for injury analysis (modified from Nahum and Gomez, Injury Reconstruction: The Biomechanical Analysis of Accident Injury, SAE Paper No. 940568). The results of the reconstruction needed for a determination of the occupant kinematics include the vehicle’s Delta-V, PDOF, and rotation rate. Delta-V (∆V) is the velocity change that a vehicle experiences as a result of the impact and depends on the magnitude of the applied force and mass of the vehicle. The Principal Direction of Force (PDOF) is the 17 | P a g e
J. Eftekhar & Associates Michael Reyes, Ph.D., BME, C.E.O TCDLA August Presentation direction of a single force that represents the net impact force applied to the vehicle. The vehicle motion resulting from the impact depends on the magnitude, direction, and point of application of the impact force with respect to the vehicle’s center-of-gravity (CG). The resulting vehicle motion may consist of translation (produced by force applied through the vehicle’s center of gravity), rotation (produced by an eccentric force), or a combination of the two (Figure 11).
Figure 11: Examples of forces which result in vehicle translation and rotation. Regarding vehicle crashes, three impacts must be considered when performing an injury analysis. The first is the impact between the vehicle and another vehicle or object. The second is the impact between the occupant and the vehicle interior. Occupants move with pre-impact velocities while impact forces change the vehicle’s velocity state. A relative velocity develops between the occupant and the interior / restraint, known as the Occupant Impact Velocity (OIV). Depending on seating position and rotation rate, an occupant’s impact velocity may be greater than, equal to, or less than the vehicle’s Delta-V. The third impact between the internal organs and the hard tissues of the body (e.g. coup-contrecoup brain injury, heart impact against the sternum). The figures below illustrate examples of occupant motion as a result of vehicle translation and rotation (Figure 12 - Figure 14).
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J. Eftekhar & Associates Michael Reyes, Ph.D., BME, C.E.O TCDLA August Presentation
Figure 12: Example of occupant motion as a result of a centered frontal impact.
Figure 13: Example of occupant motion as a result of a centered frontal impact.
Figure 14: Example of occupant motion as a result of a side impact to the right-rear quarter panel.
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J. Eftekhar & Associates Michael Reyes, Ph.D., BME, C.E.O TCDLA August Presentation The expected occupant motion resulting from an impact must be corroborated with witness marks and the injury pattern. Witness marks which indicate evidence of seatbelt use include: • • • • •
Abrasions of the webbing and plastic hardware that the webbing contacts (Figure 15). Belt found in an extended configuration. Latch plate and buckle damage. Biological and fabric materials transfer. “Seatbelt sign”: bruises or abrasions across the chest, abdomen, and neck of the occupant.
Figure 15: Abrasions to webbing and hardware. Evidence of seatbelt non-use (Figure 16) includes: • •
Contact to interior structures that cannot be achieved by a restrained occupant. A stowed seatbelt configuration where the belt is prevented from extending due to damage or a fired pretensioner.
In the case of occupant ejection during a rollover, contact evidence that may be used to rulein or out seatbelt use includes: • • • •
Deformation to roof rails Abrasions to plastic trim Transfer or entrapment of biological material (e.g. hair in window gaskets, biological material on the vehicle exterior) Deformation of exterior body panels produced as result of the ejected occupant being positioned between the exterior vehicle structure and the ground.
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J. Eftekhar & Associates Michael Reyes, Ph.D., BME, C.E.O TCDLA August Presentation
Figure 16: Evidence of seatbelt non-use. It should be noted that a belted occupant may still contact the vehicle interior under certain conditions (e.g. side impact, high-speed frontal impact; Figure 17 - Figure 18). Interior surface and component contact evidence includes: • • • •
Deformed steering wheel / stroked steering column Damaged dashboard components Windshield fracture due to interior contact Biological evidence transfer (e.g. blood, hair, tissue, DNA).
Figure 17: Examples of belted occupant interactions with vehicle interior.
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J. Eftekhar & Associates Michael Reyes, Ph.D., BME, C.E.O TCDLA August Presentation
Figure 18: Examples of belted occupant interactions with vehicle interior. Trauma to the occupant must be corroborated with the occupant kinematics and witness marks. Trauma can be characterized as blunt, penetrating, or inertial. Each is caused by the type of interaction between the body and the environment, or the inertial forces to which the body is subjected. Blunt and penetrating trauma are defined by how the force contacts the body, while inertial trauma is defined by motion of the body or its organs. There's often overlap — a car crash can produce all three types at once (e.g. blunt chest impact, penetrating injury from debris, and inertial aortic injury). Blunt Trauma is injury caused by impact from a blunt force or surface, where energy is distributed across a broad area without breaking the skin. Examples include: • • •
A driver’s chest hitting the steering wheel Head striking a pillar Door intrusion impacting an occupant’s torso.
Penetrating trauma is injury where an object pierces the skin and enters the body, creating an open wound. Examples include: • • •
Glass penetration from facial and head impacts with glazing Lacerations from damaged vehicle components Impalement on a vehicle component.
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J. Eftekhar & Associates Michael Reyes, Ph.D., BME, C.E.O TCDLA August Presentation Inertial trauma is injury caused by rapid acceleration or deceleration forces, where internal structures are damaged by differential movement rather than direct impact. Examples include: • • •
Whiplash Diffuse axonal injury Aortic tear / rupture caused by sudden deceleration
It is important to describe each injury to establish its nature, location, and severity. Anatomic, physiologic, and pathological terms are used for the injury description. The location of the injury is described in terms of the anatomical features which are injured (e.g. skin, bone, ligaments, tendons, organs, central nervous system – brain and spinal cord) and their anatomical positions. The type of injury is described in pathological terms which characterize the trauma (e.g. contusion, laceration, abrasion, rupture, fracture, hemorrhage, ecchymosis). Injury pattern diagrams are especially useful in matching each injury to areas of vehicle contact and scene evidence (Figure 19 - Figure 27).
Abdominal hematoma; Linear abrasions suggestive of seatbelt sign Right lower extremity contusions Right lower extremity abrasions
Figure 19: Injury Pattern Diagram – Superficial.
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J. Eftekhar & Associates Michael Reyes, Ph.D., BME, C.E.O TCDLA August Presentation
Right frontal scalp laceration (1.5 inch)
Racoon eyes; Pupils fixed and dilated
Laceration to the right nasolabial fold extending to chin
Figure 20: Injury Pattern Diagram – Superficial.
Roght lung contusion
Acute infarct of the upper pole of the right kidney
Figure 21: Injury Pattern Diagram - Internal Organs.
Glascow Coma Scale (EMS records): Eye opening: no response (1) Best verbal response: no response (1) Best motor response: no response (1) Total Score: 3
Moderately extensive subarachnoid hemorrhage, left greater than right
Figure 22: Injury Pattern Diagram – Central Nervous System. 24 | P a g e
J. Eftekhar & Associates Michael Reyes, Ph.D., BME, C.E.O TCDLA August Presentation
Comminuted, displaced, and angulated fractur of mid radial shaft and mid ulnar shaft Comminuted and displaced fracture of right femoral shaft
Figure 23: Injury Pattern Diagram – Skeletal.
Blowout type fractures of the left medial orbital wall and orbital floor
Figure 24: Injury Pattern Diagram - Skeletal.
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J. Eftekhar & Associates Michael Reyes, Ph.D., BME, C.E.O TCDLA August Presentation
Bilateral medial malleoli fractures
Right lateral malleolus fracture
Figure 25: Injury Pattern Diagram – Skeletal.
Fractures of the 2nd 5th metatarsal heads
Fractures of the 3rd and 5th metatarsal shafts
Fracture of the 3rd metatarsal base
Figure 26: Injury Pattern Diagram – Skeletal. VII.
Case Example: Vehicle vs. Pedestrian
Synopsis The following case illustrates the application of the foregoing principles to an analysis of the evidence produced in an intoxication manslaughter case involving a vehicle and pedestrian. The findings and opinions developed as a result of the accident reconstruction and biomechanics methodologies lead to the determination of the most plausible incident scenario leading to a reduced sentence for the Defendant. The lesson to be learned from this case is to never take the State’s interpretation of the evidence at face value. 26 | P a g e
J. Eftekhar & Associates Michael Reyes, Ph.D., BME, C.E.O TCDLA August Presentation Case Details Case Style: The State of Texas vs. Andrew Garcia Jurisdiction: 248th Criminal District Court of Harris County, Texas Charge: Intoxication Manslaughter (felony offense, maximum sentence sought by prosecutor). Disposition: Defendant received six months of probation and no jail time. Background Information and Evidence Accident Date and Time: July 11, 2017 at approximately 8:40 PM Location: Baytown, Harris County, Texas Roadway Location: N. Main Street Weather: Clear Light Condition: Dark, Lighted Roadway Condition: Dry Unit 1: 2015 Ford F-150 operated by Andrew Garcia Pedestrian: Suheiry Suyin Luzardo Barrios Investigator’s Narrative Opinion of What Happened: “UNIT #1 WAS TRAVELLING SOUTHBOUND IN THE OUTSIDE LANE OF THE 4300 BLOCK OF N. MAIN ST. UNIT #1 VEERING RIGHT AND STRUCK THE CURB. UNIT #1 THEN STRUCK SUHEIRY LUZARDO CAUSING FATAL INJURIES. UNIT #1 THEN CONTINUED SOUTHBOUND ON N. MAIN ST. UNIT #1 IS DESCRIBED AS A WHITE FORD F-150”. Figure 27, is the Crash Report Field Diagram.
Figure 27: Crash Report Field Diagram.
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J. Eftekhar & Associates Michael Reyes, Ph.D., BME, C.E.O TCDLA August Presentation The incident occurred in the area of the outside lane of southbound North Main Street, south of its intersection with West Baker Road (Figure 28). A Texaco was located adjacent to the impact area. An exterior surveillance camera on the building captured a portion of the vehicle’s pre-impact movement.
North Main Street
West Baker Road
AOI
Texaco
Figure 28: Google Earth aerial view of the crash site. On-Scene photographs documented the location of personal items, a scrape on the southbound curb, biological material on the curb and grass, and the final rest position of the pedestrian (Figure 29 - Figure 32). A crash scene diagram was prepared depicting the location of the physical evidence (Figure 33).
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J. Eftekhar & Associates Michael Reyes, Ph.D., BME, C.E.O TCDLA August Presentation
1. Sandal (left) 2. Biological material on curb and grass 3. Final rest of pedestrian 4. Scrape mark on curb 5. Sandal (right) Figure 29: On-scene photography depicting physical evidence.
Figure 30: On-scene photography depicting (a) location of the left sandal and (b) scrape on the curb.
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J. Eftekhar & Associates Michael Reyes, Ph.D., BME, C.E.O TCDLA August Presentation
Figure 31: On-scene photography depicting biological materials on the curb and adjacent grass.
Figure 32: On-scene photography depicting (a) the pedestrian final rest position and (b) location of right sandal in the Texaco parking lot.
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J. Eftekhar & Associates Michael Reyes, Ph.D., BME, C.E.O TCDLA August Presentation
Figure 33: Scaled crash-scene diagram depicting the location of physical evidence. The State presented a scenario wherein the vehicle jumped the curb and struck the pedestrian while she was walking on the grass next to the road (Figure 34 - Figure 35). A key piece of evidence used to support the State’s case was the scrape on the curb, which they concluded was produced by the vehicle.
Figure 34: Graphic depicting the impact scenario offered by the State. 31 | P a g e
J. Eftekhar & Associates Michael Reyes, Ph.D., BME, C.E.O TCDLA August Presentation
Figure 35: Graphic depicting the impact scenario offered by the State. Research of Google Maps historical street view images revealed the scrape on the curb was already present on the curb six months before and therefore could not have been related to the incident (Figure 36). Analysis of the on-scene photographs revealed no evidence of tire tracks or furrowing in the grass which would be consistent with the State’s case. Further, the State’s impact location would have most likely required that the vehicle’s right-side mirror would impact the utility pole.
Figure 36: Comparison of an on-scene photograph of the curb scrape with a Google Maps Street View image of the same scrape present months before the incident. Injury pattern diagrams were created to aid in matching the pedestrian’s injuries to the vehicle damage and the biological materials present at the scene (Figure 37 – Figure 38). The left-sided skeletal injuries are consistent with being produced by the left-front corner of the
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J. Eftekhar & Associates Michael Reyes, Ph.D., BME, C.E.O TCDLA August Presentation pickup truck. The right-sided external injuries are consistent with the pedestrian impacting the curb.
Figure 37: Injury pattern diagram depicting the location, type, and extent of the external injuries sustained by the pedestrian.
Figure 38: Injury pattern diagram depicting the location, type, and extent of the skeletal injuries sustained by the pedestrian. 33 | P a g e
J. Eftekhar & Associates Michael Reyes, Ph.D., BME, C.E.O TCDLA August Presentation
Figure 39: Vehicle damage matching to pedestrian injury pattern. (1) Front hood damage – left side body strike. (2) Top hood damage – head strike. (3) Damaged right-front fender – body strike. Having established the impact position of the pedestrian with respect to the vehicle, the pedestrian final rest location and the biological evidence on the curb and graph could be used to place the vehicle and pedestrian at an impact, thereby establishing that the pedestrian was in the road and possible crossing at a location where there was no crosswalk (Figure 40 - Figure 43).
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J. Eftekhar & Associates Michael Reyes, Ph.D., BME, C.E.O TCDLA August Presentation
Figure 40: Graphic depicting the trajectory of evidence and the most likely impact positions of the vehicle and pedestrian.
Figure 41: Graphic depicting the vehicle and pedestrian impact positions. 35 | P a g e
J. Eftekhar & Associates Michael Reyes, Ph.D., BME, C.E.O TCDLA August Presentation
Figure 42: Graphic depicting the vehicle and pedestrian impact positions.
Figure 43: Graphic depicting the vehicle and pedestrian impact positions.
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J. Eftekhar & Associates Michael Reyes, Ph.D., BME, C.E.O TCDLA August Presentation Having established the most plausible impact scenario, the next task was to apply photogrammetric analysis to the Texaco surveillance camera video to determine the vehicle’s pre-impact speed. Having identified the positions of the vehicle in two frames, the elapsed distance and time between these points could be used to calculate an average preimpact speed for the vehicle. It was found to be approximately 34 mph, which was below the posted speed limit of 40 mph (Figure 44).
Figure 44: Graphic depicting photogrammetry analysis based on surveillance camera images used in conjunction with known reference points present in the video and located at the site. Conclusions The following conclusions were instrumental in aiding the Defendant’s counsel in securing a reduced sentence: 1. Unit 1 (Garcia Jr.) clearly struck Mrs. Barrios when she was in the roadway and Unit 1 was properly established in its lane. 2. Mrs. Barrios was in violation of Texas Transportation Code Section 552.006: Use of Sidewalk (b).
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J. Eftekhar & Associates Michael Reyes, Ph.D., BME, C.E.O TCDLA August Presentation VIII.
Conclusion
The skillful use of an accident reconstructionist and a biomechanics expert in the Defense’s case can lead to profound outcomes, including sentence reductions, acquittals, and case dismissals. Practitioners of these disciplines can effectively aid the Defense attorney in discrediting the State’s experts and case. Further, by applying the appropriated methodologies of each discipline, the resulting findings and opinions inform the jury’s understanding of the involved factors and evidence and the most plausible explanation of the incident.
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Criminal Defense Lawyers Project
24th Annual Top Gun August 14, 2026 The Whitehall Houston, TX
Topic: Defending Breath and Blood DWI Cases Speaker:
Sean Darvishi The Law Office of Sean R. Darvishi, PLLC 1235 North Loop W Ste 1125 Houston, TX 77008-4711 832.766.4019 phone 713.583.2896 fax sean@defendmetexas.com email http://www.defendmetexas.com/ website
6808 Hill Meadow Dr :: Austin, Texas :: 512.478.2514 p :: 512.469.9107 f :: www.tcdla.com
DEFENDING BREATH AND BLOOD DWI CASES IN TEXAS WITHOUT HIRING EXPERTS By: Sean R. Darvishi
I. INTRODUCTION Every criminal defense practitioner knows the sinking feeling of opening a case file with a great video and finding a not so favorable breath or blood result. The standard reflex in modern Texas DWI defense is to retain an independent expert—a toxicologist, chemist, or former breath test technical supervisor—to review the underlying data and testify at trial. Maybe you get that suppression because the expert was able to get a concise explanation of the problem across to the Judge. However, retaining qualified scientific experts routinely costs thousands of dollars per case. For a vast majority of my clients, these expenses are financially out of reach. The lawyer is then left with a critical dilemma: how to effectively challenge state-sponsored scientific evidence without a defense expert on the payroll. The answer lies in understanding that the State of Texas already bears the burden of proof beyond a reasonable doubt and already employs the experts—the State Technical Supervisors and forensic toxicologists. Defense counsel does not need to hire a competing expert to win a breath or blood case. Instead, counsel must master the foundational science, utilize vivid demonstratives, and structure cross-examinations to convert the State’s own witnesses into defense witnesses. By strategically wielding peer-reviewed literature, statutory observation rules, and lab errors, defense counsel can generate reasonable doubt directly from the prosecution’s case-inchief. II. ESSENTIAL MATERIALS, INTAKE PROTOCOLS, AND TRIAL NOTEBOOK DESIGN A successful defense without an expert requires rigorous pretrial preparation and organization. Counsel must build a scientific library and establish standardized intake workflows before the case is ever set for trial. Having a building knowledge on how to beat these cases is essential but having the ability to put it in laymen’s terms is what will keep you getting two word verdicts instead of finishing in 2nd place. A. Recommended Sources Counsel should maintain access to key Texas practice guides and scientific manuals: •
Texas DWI Manual (Deandra Grant & Kimberly Tucker, James Publishing): Required reading in my office for any lawyer or intern who is going to handle a DWI case in any capacity
•
National Highway Traffic Safety Administration (NHTSA) Student and Instructor Manuals: These manuals are accessible free of charge in PDF format (e.g., via the Washington State Patrol DRE document portal). Lawyers should print and bind these manuals. State Bar of Texas membership benefits frequently include corporate discounts at Office Depot/OfficeMax for printing and binding costs.
•
TDCAA Case Law Updates (Jessica Frazier): Essential for tracking real-time appellate rulings on blood search warrants, administrative license revocations (ALR), and evidentiary suppression. You must routinely Shephardize state cases prior to trial as the State of course only puts in cases that benefit themselves.
•
Disposition of Toxic Drugs and Chemicals in Man (Randall C. Baselt): An invaluable text for drug-related DWI defense. Due to its high retail cost, you should monitor secondary markets such as eBay or Half Price Books to acquire a cheaper copy.
B. Standardized File Intake and Evaluation Case evaluation must begin immediately at intake using standardized forms: 1. DWI Client Questionnaire: Captures detailed medical histories, dietary intake, timeline of alcohol or medication consumption, physical injuries, and occupational chemical exposures. This may do very little for you at the beginning of a case but once all of the evidence is in and you are able to review the videos and the chemical tests and compare with some conditions your client may have, this can prove to be invaluable. 2. Video Evaluation Forms and Standardized Field Sobriety Test (SFST) Scoring Sheets: Standardizes the review of dashcam and body-worn camera footage against NHTSA scoring criteria. I like keeping detailed notes. It makes it very easy to go back and catch things I missed before. And makes time for trial prep very minimal. C. Timestamp Evidence Review and File Management Preparation begins well before trial setting. Counsel must execute a written review of all digital media, establishing a granular timeline with exact timestamps. •
Timeline Indexing: Document exact times for the initial traffic stop, officer contact, SFST administration, arrest, the 15-minute statutory observation period, and the breath or blood draw.
•
Redaction Times: If you are keeping track of what a redaction should be while first looking at the video it gives you a much clearer idea of what to look for
•
Issue-Specific File Structure: When a specific technical issue is identified, counsel should immediately clone relevant research papers, white papers, or presentation slides into a dedicated subfolder within the digital case file. Counsel should draft a brief working memorandum in Microsoft Word summarizing the legal and scientific theory while the facts are fresh.
D. Digital Trial Notebook Architecture I believe every lawyer should construct a standardized, cloud-based trial notebook (e.g., via Dropbox) for your practice. As you find a new issue you create a subfolder and then file the new case you found away. You can even make more subfolders which will show cases that are good for the state or cases that are good for the defense. It should contain distinct folders for voir dire outlines, cross-examination examples, scientific white papers, demonstrative exhibits, case law and motions. III. VOIR DIRE STRATEGIES: DEMYSTIFYING SCIENCE WITHOUT AN EXPERT Jury selection sets the scientific frame for the defense. You must demystify technical terminology, address the State's resource imbalance, and establish common-sense scientific principles before any evidence is introduced. A. Highlighting the State's Resource Advantage You should subtly impress upon the panel that the State of Texas possesses vast financial and institutional resources. Remind prospective jurors that if an individual citizen wants to hire an independent analytical chemist or toxicologist, it costs thousands of dollars out-of-pocket. Contrast this with the prosecution, which has full-time access to state crime laboratories, technical supervisors, and forensic toxicologists funded by taxpayer dollars. But do it in a way that is smooth and not just grandiose for no reason. B. The "Translate and Elevate" Technique To establish immediate credibility with the panel, counsel can explain a complex physiological process using an everyday analogy, and then immediately attach the precise scientific terminology. •
The Keto/Diabetic Analogy: Ask the panel if anyone is familiar with the smell associated with strict ketogenic diets or diabetic ketoacidosis. Jurors will typically describe a distinct chemical or acetone-like odor on the breath.
•
Executing the Pivot: Once a juror confirms this familiar occurrence, counsel explains that the body is converting fats into ketones and producing endogenously generated acetone. By connecting a relatable physical observation to its scientific term,
counsel demonstrates authoritative knowledge of the subject matter without needing a paid expert to testify to it. C. Neutralizing the "CSI Effect" Argument Prosecutors frequently attempt to lower their burden of proof during voir dire by warning jurors, "This isn't CSI; real law enforcement does not have Hollywood technology." Counsel should immediately adopt and reframe this argument: "The State is right—this isn't a television show. But this isn't a traffic ticket either. The State is asking you to rely on complex chemistry and computerized testing instruments to convict a citizen. If the prosecution relies on forensic science to meet its burden of proof beyond a reasonable doubt, that science must be executed flawlessly." Don’t let the state get away with things like that which will end up demeaning your defense. IV. PRETRIAL ENGAGEMENT: CONVERTING THE STATE'S EXPERT The core strategic pillar of defending a DWI without a defense expert is simple: Turn the State’s expert into your witness. A. Advance Transmittal of Scientific "White Papers" You don’t have to withhold scientific authority until cross-examination. Well in advance of trial, you can forward relevant peer-reviewed scientific studies ("white papers") directly to the State’s Technical Supervisor or forensic toxicologist. When defense counsel engages the State’s analyst in technical discussions prior to trial, two strategic objectives are achieved: 1. Credibility Establishment: The analyst recognizes that defense counsel understands the underlying chemistry and analytical testing protocols, preventing the witness from relying on scripted, evasive answers on the stand. 2. Evidentiary Concessions: An analyst who realizes counsel is thoroughly prepared is far more likely to concede known scientific limitations on cross-examination—such as breath temperature variance, rising blood alcohol, and margins of error. By establishing professional rapport with the analyst prior to trial, counsel gains a structural advantage over prosecutors who may only understand surface-level direct examination questions.
V. DEFENDING BREATH TEST CASES (INTOXILYZER 9000) Jurors respond to visual aids and tangible physical demonstrations. When challenging infrared breath testing without an expert, counsel must rely on administrative rule violations, physiological variables, and physical demonstratives. A. The 15-Minute Observation Period Violation Under the Texas Administrative Code (Title 37, Part 1, Chapter 9, Subchapter A), a breath test operator must observe the subject for a minimum of 15 continuous minutes prior to testing to ensure the subject does not ingest contaminants, belch, or vomit. •
Video Review: Conduct a second-by-second review of the breath test room video or dash and/or body camera. Document every instance where the operator turned their back, left the room, or engaged in administrative paperwork while out of visual contact with the client. Watch “The 21 minute video” for examples of what a violation would be
•
Technical Supervisor Profiling: Counsel must evaluate the tendencies of the local Technical Supervisor (TS): 1. The Sponsoring TS: Will attempt to sponsor the test results regardless of procedural irregularities, claiming minor observational gaps have "no scientific effect." 2. The Non-Sponsoring TS: Will acknowledge that strict adherence to administrative rules is a prerequisite for scientific reliability and will refuse to validate a compromised test.
•
Suppression Under CCP Art. 38.23: Counsel should request a hearing outside the presence of the jury pursuant to Texas Rule of Evidence 705. Argue that breath evidence obtained in violation of state administrative regulations must be excluded under Texas Code of Criminal Procedure Article 38.23(a). You should be aware of the State’s reliance on Article 38.23(b), which is the good-faith exception.
B. Breathing Patterns and the "Hyperventilation/Breath-Holding" Effect Landmark research published by Dr. A.W. Jones (Physiological Aspects of Breath Alcohol Measurement, Journal of Alcohol, Drugs and Driving, 1990) demonstrates that holding one’s breath prior to blowing into an instrument can falsely elevate measured BAC by up to 15%. If police body camera footage shows the officer commanding the client to "take a deep breath, hold it, and blow until I tell you to stop," counsel can establish that officer instructions artificially inflated the final result.
C. Breath Temperature Flaws and Demonstrative Proof Infrared breath instruments in Texas calibrate results under the assumption that human exhaled breath is delivered at a constant temperature of 34° Celsius (93.2° Fahrenheit). However, human breath temperature varies significantly based on physiology, body temperature, and physical exertion. •
The Scientific Formula: Peer-reviewed literature establishes that for every 1°C increase in exhaled breath temperature above 34°C, the breath test overestimates BAC by approximately 6.5%.
•
The Alabama Study: Research by Dale A. Carpenter and James M. Buttram (IACT Newsletter, 1998) analyzing breath temperatures using a Draeger Alcotest MK III revealed that 93% of tested subjects exhibited breath temperatures exceeding 34°C, with a mean temperature of 34.9∘ C. Under an Intoxilyzer instrument lacking temperature sensors, this average temperature deviation results in a 6.5% systemic inflation of the subject's reported BAC.
•
In-Court Jury Demonstration: To explain breath temperature dynamics without an expert, ask the jury to perform a simple exercise: hold a hand in front of the mouth, open wide, and exhale slowly (warm breath). Then, have them purse their lips and blow rapidly across their hand (cool breath). This physical sensation illustrates to the jury how breath delivery mechanics alter exhaled temperature and air density.
D. Range of Error: Accuracy vs. Precision Department of Public Safety (DPS) Technical Supervisors are specifically trained to avoid the term "margin of error" and to refer to testing equipment as "instruments" rather than "machines." •
Quantifying the Error: In Texas, a breath instrument is considered to be operating within acceptable scientific parameters during calibration checks if its results fall within ±0.02 of the first blow. For a test reading of 0.08, an acceptable tolerance of 0.06 to 0.10 represents a 25% range of error.
•
Cross-Examination Strategy: Force the Technical Supervisor to admit the technical difference between accuracy (hitting near a target) and precision (reproducible exactness). Establish that while the instrument may meet broad state calibration tolerances, it lacks the scientific precision required to state an exact BAC reading without an associated error boundary.
F. The Acetone and Ketone Interference In May 2014, the Breath Alcohol Advisory Board revealed that the Intoxilyzer 9000 does not subtract acetone from its analytical calculation. While the manufacturer claims the instrument can detect certain interferents such as toluene and acetaldehyde, endogenous volatile organic compounds—such as acetone produced by individuals on ketogenic diets, diabetics experiencing ketosis, or workers exposed to solvent vapors in nail salons—can absorb infrared light at similar wavelengths, resulting in falsely elevated BAC scores.
VI. DEFENDING BLOOD TEST CASES (HEADSPACE GAS CHROMATOGRAPHY) Blood alcohol concentration in Texas criminal prosecutions is evaluated via Headspace Gas Chromatography with a Flame Ionization Detector (HS-GC-FID). Chromatography is a physical science of separation. When defending a blood case without an expert witness, counsel must avoid getting bogged down in minor technical disputes that do not resonate with a jury. Instead, focus heavily A. Explaining Gas Chromatography to a Jury You must translate gas chromatography into intuitive visual models: •
The Mall / Conveyor Belt Analogy: Compare the chromatography column to a crowded shopping mall. A group of shoppers enters the mall at the exact same moment. Different shoppers travel at the same speeds but tend stop at different stores based on their individual traits. Even though they entered together, they exit the mall at distinct, predictable times.
•
The Classroom Race Analogy: Picture a teacher lining up students at the back of a classroom and timing how long it takes each student to run across the room and step outside into the heat. Each child has a predictable "finish time" (retention time).
VII. DEFENDING DRUG-BASED DWIs (BLOOD TOXICOLOGY) When blood analysis returns negative for alcohol but reveals the presence of prescription drugs or illicit substances, the prosecution will pivot to a theory of impairment by drugs. A. Presence Does Not Equal Impairment
The central tenet of defending drug-based DWIs is that the qualitative presence of a drug or metabolite in blood does not prove impairment at the time of driving. •
Therapeutic Tolerance: Patients who take prescription medications (such as longterm pain management drugs, benzodiazepines, or ADHD treatments) under medical supervision develop therapeutic tolerance. The detection of a therapeutic blood concentration proves drug exposure, not loss of normal mental or physical faculties.
•
Marijuana / Cannabis Pharmacokinetics: Tetrahydrocannabinol (THC) is highly lipophilic (fat-soluble). In frequent or chronic users, inactive metabolites (such as THC-COOH) and low levels of active Delta-9 THC persist in the vascular system days after psychoactive effects have entirely subsided. Blood concentrations of THC do not correlate reliably with real-time impairment.
B. The Five Pillars of Toxicologist Cross-Examination When cross-examining the State’s forensic toxicologist without a defense expert, counsel must structure the examination around five core concepts: 1. Half-Life and Pharmacokinetics: Require the toxicologist to explain distribution and elimination half-lives, establishing that drug concentrations drop rapidly during the post-absorptive phase. 2. Pharmacodynamic Characteristics: Require the witness to classify the substance (e.g., central nervous system depressant, stimulant, or analgesic) and admit that therapeutic ranges are designed to allow patients to function normally. 3. Peer-Reviewed White Papers: Bring authoritative literature directly to the podium, including NHTSA’s Drugs and Human Performance Fact Sheets. 4. Analyst Tendencies: Identify whether the assigned toxicologist has a documented history of testifying beyond the scientific consensus or whether they will concede therapeutic boundaries. 5. Managing Public Perception: Address drug stigma during voir dire to ensure jurors separate the legal consumption of prescribed medication or past exposure from realtime impairment. VIII. CONCLUSION Defending a breath or blood DWI charge in Texas without hiring an expert witness is neither a compromise nor a handicap. It can be an intentional trial strategy centered on mastering the prosecution's scientific evidence.
By utilizing clear physical analogies in voir dire, enforcing administrative regulations, exploiting instrument tolerance limits, and conducting rigorous cross-examinations on sample preparation and pharmacokinetics, defense counsel can dismantle the State's forensic evidence. The State bears the burden of proof beyond a reasonable doubt; by turning the prosecution’s analysts into defense witnesses, defense counsel can effectively expose scientific doubt without burdening the client with expert witness fees.
Criminal Defense Lawyers Project
24th Annual Top Gun August 14, 2026 The Whitehall Houston, TX
Topic: DWI Judo: Using the Officer’s Own Manual Speaker:
Chris McKinney Murphy & McKinney Law Firm, P.C. 902 Heights Blvd. Houston, TX 77008 281.435.9803 phone 713.583.0205 fax chris@dougmurphylaw.com email http://www.dougmurphylaw.com/ website
6808 Hill Meadow Dr :: Austin, Texas :: 512.478.2514 p :: 512.469.9107 f :: www.tcdla.com
Texas Criminal Defense Lawyers Association 24th Annual Top Gun DWI Houston, Texas August 14, 2026
DWI Judo: Using the Officer’s Own Manual to Beat SFSTs and Breath Tests
Christopher M. McKinney Murphy & McKinney Law Firm, P.C. 902 Heights Blvd. Houston, Texas 77008 713-229-8333 chris@dougmurphylaw.com
The National Highway Traffic Safety Administration (NHTSA) sponsored field sobriety tests manual is simultaneously the officer’s claimed source of authority and a driving while intoxicated defense practitioner’s single best tool on cross-examination. But police officers cannot have it both ways. They can either follow the manual and be subject to the manual’s own limitations, or they can choose not to follow the manual, rendering the results meaningless because they are no longer standardized. Non-standardized tests are irrelevant. The backbone of the alleged reliability of these field sobriety tests rests solely on their standardized nature. Starting in 1975, NHTSA sponsored studies that produced what we now know as the three standardized tests that are in nearly every DWI arrest. These studies, completed under controlled conditions, produce the accuracy rates that prosecutors love to cite—77% for the Horizontal Gaze Nystagmus (HGN) test, 68% for the Walk and Turn (WAT) test, and 65% for the One Leg Stand (OLS) test, each individually.
These accuracy percentages were obtained from “experienced” SFST
personnel. Validation, however, only applies when the tests are administered in the prescribed manner, using standardized clues and standardized criteria. Indeed, “if any one of the SFST elements is changed, the validity [of the test] may be compromised.” (NHTSA Student Manual 2023, Session 8, Page 12). These tests were designed as arrest decision tools for police officers on the street, not as proof beyond a reasonable doubt of intoxication for juries. The decision point thresholds—4 out of 6 clues on HGN, 2 out of 8 clues on WAT, and 2 out of 4 clues on OLS- were created to help an officer decide whether to arrest a driver, a far lower standard than necessary to convict someone of a criminal offense. The NHTSA manual itself states
that SFSTs are not pass/fail tests. Yet in courtrooms across this country, prosecutors ask officers whether the defendant passed or failed, and officers, who are trained on the very manual that says otherwise, answer that the defendant failed. The government takes a probable cause tool built to help officers make arrest decisions and presents it to juries as proof beyond a reasonable doubt. This article is intended to provide the DWI practitioner a powerful primer on SFSTs, pinpoint where officers go wrong in their SFST performance and grading, show you how to attack them, and provide practical checklists you can take to court Monday morning. Start by getting your own copies of the NHTSA Student and Instructor Manuals, which are both provided in the materials accompanying this article. Know the Manuals Cold There are two manuals the DWI practitioner needs to familiarize themselves with. First, the NHTSA Participant Manual. This is the baseline, the protocol, what the officer was supposed to do. Second, the Instructor Manual. It is the coaching guide for the people who train the officers. It contains something the Participant Manual does not— the lists of common mistakes that instructors are told to watch out for and correct. When an officer makes one of these mistakes in the field, the DWI practitioner is not nitpicking; they are identifying exactly what an officer’s instructor warned them about during training. The manuals also tip off the officers to you. It tells them what to expect. Officers are warned that they may be asked questions that “may suggest you eliminated portions of the tests or gave incomplete or confusing instructions.” (Session 11, Page 27). The same standardization they beat their chests to that supports the tests’ credibility and
consistency also cuts against them when that standardization is not followed. The officer’s training sets up your argument against their tests. Officers are also told how to phrase the work (or lack thereof) in their investigations. They are taught to avoid saying they “didn’t do XYZ” and instead say they “couldn’t do XYZ,” because “didn’t” implies choice, while “couldn’t” implies necessity. (Session 11, Page 27). Making a choice not to do a test in a certain manner is a failure in an investigation and is golden on cross-examination. Their own training tells officers that this distinction matters. Make them own it. Their written reports and how they are taught to write them are also ripe areas of cross-examination. What these reports say matters. But what they leave out can matter more. Simply listing the number of clues on a test, however, is not enough. Officers “must be able to describe how the subject performed on the tests and what the subject did.” (Student Manual, Session 8, Page 54). An officer who testifies to 6 out of 6 clues on HGN without describing what was observed has not met the officer’s own training standards. Push the officer to describe each clue specifically and watch whether their description matches the manual’s definition. Often, it does not. An officer’s report must also be consistent. (Student Manual Session 11, Page 22). Any differences must be adequately explained. Officers are put on alert that the defense will attempt to impeach them by pointing out “seemingly minor inconsistencies.” When testimony does not match the report, or the report does not match the video, the DWI practitioner is not manufacturing inconsistencies; they are doing exactly what the manual warned they would do. The manual has told them to be detailed and consistent. Hold them to their training.
With the NHTSA Participant and Instructor Manuals in hand, let’s walk through each test, what the manual requires, and where officers deviate. Horizontal Gaze Nystagmus Police officers are trained that nystagmus is the involuntary jerking of the eyes. HGN specifically is that jerking as a person’s eyes gaze to the side. The NHTSA manual refers to this as “the first and most accurate test in the SFSTs.” (Student Manual, Session 8, Page 18). HGN, however, is not a divided attention test. Only the WAT and OLS tests fit that criterion. (Student Manual, Section 7, Pages 8-10).
HGN is a physiological,
involuntary response, meaning the subject is not “doing” anything. They are simply following a stimulus with their eyes. Officers routinely lump all three tests together, despite HGN not fitting the divided-attention test criteria. What HGN Is, and What it Isn’t Nystagmus, however, is not always caused by alcohol or other intoxicants. The NHTSA manual lays out three categories of nystagmus beyond alcohol impairment. Vestibular nystagmus includes rotational, post-rotational, caloric, and positional alcohol nystagmus (PAN). The manual’s discussion of PAN acknowledges alcohol causes it but says that proper head positioning should prevent it. An alternative is that improper head positioning could produce it, regardless of impairment level. (Session 8, Page 14-15). Neural nystagmus has a few causes. First, optokinetic nystagmus is caused by watching strobe lights, rotating lights, or rapidly moving traffic in proximity. This is commonly the emergency lights on the officer’s patrol car or passing highway traffic. Second, there is physiological nystagmus, which means it happens to everyone all the time and is too small to see. And finally, gaze nystagmus.
(Session 8, Page 16).
There is also
pathological nystagmus, which is caused by brain tumors, brain damage, and diseases of the inner ear. (Session 8, Page 20). The manual also recognizes resting nystagmus, which “usually indicates a medical condition or high doses of a Dissociative Anesthetic drug.” (Session 8, Page 19). The manual acknowledges that those with “constant and long-standing nystagmus may be able to detect and extract visual information between successive eye movements. Therefore, while the appearance to the officer may be abnormal, the person is not necessarily impaired.” (Session 8, Page 20). How HGN Must be Administered and Where Officers Go Wrong There are ten administrative steps in the proper administration of the HGN test. Step 1 – Check for eyeglasses. The Instructor Manual says that glasses may impede peripheral vision and the officer’s ability to observe the eye. (Instructor Manual, Session 8, Page 27). Step 2 – Verbal instructions. Were they given? Were they given correctly? Step 3 – Position the stimulus 12-15 inches from the nose, slightly above eye level. The Instructor Manual flags that “holding object too close to (or too far from) suspect’s eyes” as a common mistake (Session 8, Page 37). This is observable on video. Step 4 – Check for equal pupil size and resting nystagmus. If a person’s pupils are noticeably unequal, the subject may have a prosthetic eye, a head injury, or a neurological disorder. (Session 8, Page 22). If resting nystagmus is present, it usually indicates a medical condition. (Session 8, Page 22). Indeed, “if there are any abnormal findings on the pre-test checks, the officer may choose not to continue with the testing. If HGN testing is continued, officers are reminded this does not follow the standardized
protocol and should acknowledge such in any report.”
(Session 8, Page 22, 26).
Therefore, officers who found something abnormal with a person’s eyes and kept going without documenting it in their reports deviated from the manual’s own definition. Step 5 – Check for Equal Tracking. The officer should move the stimulus from the center to the far right, then to the far left, and back. "There should be a clearly distinguishable break between the check for ET tracking and lack of smooth pursuit." (Session 8, page 26). If both eyes don't track together, there's a possibility of a serious medical condition or injury. (Session 8, page 2). The manual calls this portion a "medical assessment." Those are its words, not yours. Step 6 - Lack of Smooth Pursuit (Clue 1). Stimulus moves from the center to the side in approximately 2 seconds. At least two complete passes are required according to the manual. (Session 8, page 32). The Instructor Manual flags moving an object too slowly or too quickly toward the side, failing to move the object far enough to the side, and curving downward and curving around as common mistakes officers make in administering this test. (Instructor Manual, Session 8, page 37). Step 7 - Distinct and sustained nystagmus at maximum deviation (Clue 2). Hold the stimulus steady at a maximum deviation for a minimum of 4 seconds. (Session 8, pages 33-34.) The Instructor Manual states that 4 seconds is a relatively long period of time and that officers cannot simply hold the eye to the side for an instant and expect to observe distinct jerking. (Instructor Manual, Session XX, page 38.) The manual states certain common mistakes, including not bringing the eye sufficiently far to the side and not holding the object steadily for at least 4 seconds. (Instructor Manual, Session 8, page 40.) The manual also distinguishes distinct and sustained nystagmus from fatigue
nystagmus, which occurs when eyes are held at maximum deviation for 30 or more seconds. (Session 8, page 34.) The single most important gist regarding distinct and sustained nystagmus in this portion is that the manual states, "If you think you see only slight nystagmus at this stage of the test or if you have to convince yourself nystagmus is present, then it isn't really there." (Session 8, page 34.) Step 8 - Onset of nystagmus before 45° (Clue 3). The stimulus moves from the center to 45° in approximately 4 seconds or more. (Session 8, page 37.) This is the slowest pass and the one officers most commonly rush. The Instructor Manual flags officer mistakes occurring from moving the stimulus too fast and tending to stop short of 45° as common mistakes. (Instructor Manual, Session 8, page 41, 46.) The officer is required to stop when they see jerking, hold the stimulus steady, and verify that the jerking continues. If the jerking stops when the stimulus stops, the officer hasn't found onset, and they must resume the test. (Session 8, page 37). Step 9 - Total the Clues. Each eye is checked for all three clues, for a maximum score of six. Each eye must be checked at least twice for each clue. The instructor manual warns officers to place their checkmarks in the columns corresponding to the eye being checked (Instructor Manual, Session 8, page 69). Step 10 - Check for vertical nystagmus. Note that "VGN" was not examined in the original research that led to the validation of the standardized field sobriety tests (Instructor Manual, Session 8, page 49). It's simply not part of the validated battery of tests.
Each one of these requirements is checkable on body camera footage or dash camera footage. It is easy to determine whether an officer has fulfilled his obligation regarding the timing of this test with access to video timestamps. It's also possible to estimate the stimulus distance and count the passes that an officer makes. The video either shows compliance with NHTSA's standards, or it does not. Admissibility – Legal Framework Emerson v. State, 800 S.W.2d 759 (Tex. Crim. App. 1994), established that HGN is scientific evidence and not simply a lay opinion. Because it's scientific evidence, it's governed by Rule 702 and satisfied the three prongs established by Kelly v State, 824 S.W.2d 568 (Tex. Crim. App. 1992): 1. There is a valid underlying theory. 2. A valid technique. 3. The technique was properly applied in this case. The valid technique is the NHTSA protocol. The officer must have followed it. Emerson also set the qualification standard that a practitioner-certified officer can testify about HGN performance but cannot correlate it to a specific blood alcohol concentration. As these are field tests, slight deviations from the NHTSA protocol may occur. However, Texas case law has said that slight variations affect the weight of the test, not its admissibility. This is the escape hatch prosecutors will use for every deviation in test administration that you identify. Therefore, the goal is to identify more than slight deviations or create a situation where an officer identifies that their lack of adherence was more than a slight deviation.
Don't fight the science on prong one. Don't fight the technique on prong two. Fight the application on prong three. However, make the state prove the officer followed the protocol. File your motion to suppress or your Rule 702 objection focused on the third prong of Kelly. Walk and Turn The WAT test is fundamentally different from the horizontal gaze nystagmus test. The WAT, like its sister test of the OLS stand, is a divided attention test. It requires the subject to do a mental and physical task simultaneously, which the manual says mimics the divided attention that driving demands. (session 7, page 8). Unlike HGN, which is involuntary and physiological, WAT requires active participation. This distinction matters because WAT performance is affected by everything HGN is not, including nerves, fatigue, physical condition, environment, footwear, and whether the officer gave clear instructions. The Test and Its Requirements The Walk and Turn is divided into two stages: the Instruction stage and the Walking stage (Session 8, page 41). Both can generate clues. This is important because it means the test is being scored before the subject takes a single step. A person who breaks heelto-toe stance while listening to instructions has already picked up a clue, and a person who started walking before being told to begin has picked up another. Neither of these clues has anything to do with balance or coordination. They are attention and comprehension clues, scored while the subject stands in an unnatural position on the side of a highway trying to process oral instructions from a stranger.
There are exactly eight clues. Each clue can only be counted once, no matter how many times the behavior occurs (Session 8, page 58). 1. Cannot keep balance while listening to instructions - feet must break apart. Sway or arm movement while maintaining heel-to-toe position is not this clue. 2. Starts too soon - this clue can only be recorded if the officer told the suspect not to start until directed (Instructor Manual, Session 8, page 55). If the officer skipped that instruction, this clue is invalid. 3. Stops while walking - walking slowly is not stopping (Session 8, page 45). The Instructor Manual adds that a stop should be clear and deliberate and that the officer needs to articulate the suspected reason for the stop in their report (Instructor Manual, Session 8, page 55). 4. Does not touch heel-to-toe - a gap of 1/2 in. or more between heel and toe on any step (Session 8, page 45). Less than 1/2 in. is not a clue. 5. Steps off the line - a person's foot must be entirely off the line for this clue to be counted (Session 8, page 45). 6. Uses arms to balance - a person's arms rise from their sides 6 inches or more for this clue to be counted (Session 8, page 45). Less than 6 in. is not a clue. The Instructor Manual also notes it is often possible to note two of these clues simultaneously (Instructor Manual, Session 8, page 56). This is fine, but officers sometimes double-count instead of noting two distinct clues. 7. Improper turn - this is counted when the subject removes their front foot from the line while turning, doesn't follow the turn instructions, spins or pivots, or loses balance while turning (Session 8, page 45). Here's the nuance from the Instructor
Manual: if the subject took a wrong number of steps resulting in a turn on the wrong foot and the turn itself was executed using small steps as instructed without losing balance, that's counted as an incorrect number of steps clue, not an improper turn clue (Instructor Manual, Session 8, page 56). Officers who score both are double counting. 8. Incorrect number of steps - this is when more or fewer than 9 steps in either direction are taken by the suspect (Session 8, page 45). This is about the physical steps taken and not the verbal count. "Mistakes in the verbal count do not justify recording this clue" (Instructor Manual, Session 8, page 56). An officer who scores this clue because the subject counted wrong but took the correct number of steps has gone beyond the manual. The decision point for the WAT test is two or more clues, and the manual states that the officer will accurately classify 79% of subjects (Session 8, page 47). That means 21% of the time this test gets it wrong under ideal controlled conditions administered by experienced SFST personnel. The Manual’s Limitations The original research recommended the test be performed on a dry, hard, level, non-slippery surface under relatively safe conditions. If those conditions aren't met, the manual recommends either removing the subject elsewhere or administering only the HGN test. The manual also warns that individuals over 65 years of age and people with back, leg, or inner ear problems had difficulty performing this test in the original studies (Session 8, page 41). In the original studies, less than 1.5% of subjects were over the age of 65.
The instructor manual adds that excessive weight is a factor (Instructor Manual, Session 8, page 61). The manual says officers should ask whether the subject has physical problems or disabilities before administering this test (Instructor Manual, Session 8, page 51). Did your officer ask these questions? Footwear: subjects with heels over 2 in. or any other form of unusual footwear should be allowed to remove that footwear before the test (Instructor Manual, Session 8, pages 51 and 61). What type of footwear was your client in? Heels, boots, flip-flops? Was your client offered the opportunity to remove them? The instructor manual also tells students or instructors to "remind participants to face the driver away from potential distractions that could be raised later" (Instructor Manual, Session 8, page 17). That's the manual acknowledging that environmental distractions are a legitimate defense challenge, whether it is flashing emergency lights or passing traffic on uneven ground. Where Officers Go Wrong There are common failures that officers will commit. It is important to review every second of every video and scrutinize the reports and testimonies of officers to ensure that your client's test was administered and scored properly. It is important to note during the instruction phase whether it was scripted correctly, whether the officer demonstrated it correctly, and whether they told the subject not to start until directed. If these weren't done, the test started too soon. The clue is gone, and the instruction stage itself was nonstandardized.
It's also important to determine whether your officer is correctly identifying clues or scoring things that aren't there. Looking unsteady or seeming confused are not clues. The clues are specific and defined in the manual, and if an officer testifies to observations outside those eight, they're going beyond the validated test. This is also true if an officer double-counts a clue, meaning they score the same behavior under two different clues. The wrong-foot turn scenario in the Instructor Manual is a classic example of this. Finally, each clue has a measurement, and the clue may be counted only if a subject crosses a certain threshold. This is evident in the half-inch threshold during the heel-to-toe portion and in raising arms at least 6 in. These are specific, and it is imperative to ask the officer how they measured. The manual states that the test "may lose its sensitivity if it is repeated several times" (Session 8, page 46). Therefore, if the officer made the subject start over, the retest is less reliable, according to the manual's own admission. Each of these areas comes from the officer's own training materials. You're not bringing outside experts or new arguments. You're holding the officer to the standard that they were trained on. One Leg Stand Test Like the WAT test, the OLS stand test is a divided-attention period. It is split into two stages: the instruction stage and the balance-and-counting stage (Session 8, page 49). Both stages matter. The Test and Its Requirements There are exactly four clues:
1. Sways while balancing - this is counted when a subject sways from side to side or back and forth or with a motion of their foot (Session 8, page 51). There's a critical qualifier: "Slight tremors of the foot or body should not be interpreted as swaying" (Session 8, page 51). The instructor manual reinforces this by stating, "Swaying means a distinct, noticeable side-to-side or front-to-back movement" (Instructor Manual, Session 8, page 64). Officers who score normal nervousness or minor trembling as sway are going beyond the clue definition. 2. Uses arms to balance - this clue is counted when the subject's arms move 6 or more inches away from their sides (Session 8, page 51, Instructor Manual, Session 8, page 65). This is the same measurement threshold as the WAT test. 3. Hopping - the subject keeps one foot off the ground but hops to maintain their balance (Session 8, page 52). This clue is relatively straightforward, harder to attack on definition. The suspect is trying to keep their foot up as instructed, but they're struggling with the test, not refusing it. 4. Foot down - the subject cannot maintain the OLS position (Session 8, page 52). If the subject puts their foot down, the manual says to give instructions to pick the foot up again and continue counting from the point where the foot touched (Session 8, page 52). It's important to determine whether the officer gave that instruction and, if not, whether the subject stopped. The officer has now deviated from the protocol. The decision point for this test is two or more clues. When you think about this from a percentage standpoint, with a total of only four clues, a sway and a foot-
down clue have caused the subject to meet the arrest decision threshold (versus needing only 25% of the available clues for the arrest decision on the WAT test). The Manual’s Limitations The population limitations are broader than the WAT. The manual adds a category: people who are overweight by 50 or more pounds may have difficulty performing this test (Session 8, page 49). That's the manual's own language. Combined with the same age limitation of over 65 years of age, the same physical limitation listed (including back, leg, or inner ear problems), and the same footwear issue, the list of people the manual says may have trouble with this test is substantial. Even more alarming is that there was no data containing the weight of the test subjects included in the final report (Session 8, page 49). This test was validated without ever recording the subject's weight, and so its accuracy comes from a population whose physical characteristics are partly unknown. The officer must ask about any physical problems or disabilities before administering this test, and the instructor manual says they should. (Instructor Manual, Session 8, page 51). The instructor manual also says to consider age and excessive weight, along with environmental factors, location, injury, or physical ailments, and that the importance of the totality of all factors should not be overlooked (Instructor Manual, Session 8, page 61). The Timing Problem Time is critical to this test in a way that it isn't for the HGN or WAT tests. The manual states that the original SCRI research showed that a person with a BAC above 0.10 can maintain their balance for up to 25 seconds, but seldom as long as 30 seconds
(Session 8, page 52). This is a 30-second time test, and the instructor manual says the test should be discontinued after 30 seconds (Instructor Manual, Session 8, page 65). There are really three avenues of attack here: 1. This test is calibrated to the point of expected failure. This test runs 5 seconds longer than the manual says an impaired person can typically hold. 2. If the officer let the test run past 30 seconds, they've deviated from the protocol, and any clues observed after 30 seconds are outside the validated test. 3. If the officer cut it short, you don't know whether the subject would have completed the full 30 seconds. It's also worth noting that the instructor manual says that it's possible to note two clues simultaneously and gives examples of hopping and swaying and foot down and arms raised (Instructor Manual, Session 8, page 65). Where Officers Go Wrong Again, a careful review of the video evidence in this case would show whether the officer gave complete instructions. Certain instructions must be given and certain responses that the subject must give before continuing, as the Instructor Manual requires (Instructor Manual, Session 8, page 62). An officer who launched into the test without confirming the subject's understanding has deviated from their training. One of the most common scoring errors on the OLS stand test is an officer who treats a slight tremor as a sway. The manual draws a clear line, and officers routinely ignore it. Slight tremors are not sway. If the officer
cannot articulate the difference between what they saw and a slight tremor, then this clue has not been established. Being a 30-second test, was the test actually conducted for 30 seconds? It is easy to determine from video timestamps whether this was done. Also important is the same 6-inch arm question as the WAT test. Asking an officer how they measured that distance or whether they know this threshold at all is important. Finally, if the subject put a foot down and the officer did not tell them to pick it back up and continue counting, the officer did not follow the manual’s own procedure for that situation. The officer didn't follow the manual's own procedure for that situation. Everything here comes from the officer's own training. You are simply reading their manual. They have established their own rubric, and it's your turn to grade their paper. Breath Testing – Practical Attacks Breath testing is the conclusion of the DWI officer’s investigation. If you’re dealing with a breath test, more than likely, the officer has already made up their mind. But the client’s fate is not yet sealed. There are still multiple avenues of attack on the breath test that can win the day, including whether the 15-minute observation period was observed, any physical conditions that may affect breath testing, and the machine itself. The 15-Minute Observation Period Whether or not the observation period was followed is the strongest breath test attack because it is entirely procedural and easy for a jury to understand. The regulations require that a certified breath test operator remain in the continuous presence of the subject for at least 15 minutes immediately before the test. (Breath Alcohol Operator Manual, pages 10, 25). Only certified operators can conduct this waiting period. The
period must restart if the subject places any substance in their mouth or leaves the operator’s presence at any point during the 15 minutes or during the test itself. (BAOM, pages 10, 25-26). The manual says that “direct observation is not necessary to ensure the accuracy of the test result.” (Breath Alcohol Operator Manual, pages 25-26). That language is a double-edged sword. It means that an officer can satisfy the requirement without eyes on the subject the entire time. Still, it also means that during those 15 minutes, a subject can belch, burp, regurgitate, have acid reflux, or place something in their mouth that direct observation would have caught. The requirement exists to ensure that there is no residual mouth alcohol that can artificially inflate the result. If the officer was not actually watching the subject, they cannot testify that nothing happened. The biggest determination that needs to be made is when the 15-minute observation period began. Is the officer beginning the observation period in the back of his patrol car? If so, the officer’s eyes were on the road, not your client. They were driving a car. They may have been on the radio, filling out paperwork, or talking to dispatch. And so, while the continuous presence requirement may have been met during that car ride, an officer’s focus was not necessarily on your client. Sometimes the entire 15-minute observation, or lack thereof, is captured on video. But many times, the operator says that the observation occurred in an area not covered by cameras. The second situation is harder to deal with, but there are other ways a DWI practitioner can determine certain timelines. It is therefore imperative to get all videos, all dispatch records, and any logs of when the officer reached the breath test facility to determine whether it was possible for that 15-minute observation period to occur at all.
Physical Conditions That Affect Breath Testing GERD and acid reflux can push stomach contents, including alcohol vapor, into the mouth, creating residual mouth alcohol that inflates a subject’s results. This is exactly what the 15-minute observation period was supposed to catch. But if the officer was not watching closely, it does not. The same can be said for dental work, including bridges, caps, dentures, and sometimes tongue piercings, which can also trap alcohol in the mouth and release it during the breath sample, again inflating the result. Certain respiratory conditions like asthma, COPD, and emphysema can affect breath volume and flow rate. The Intoxilyzer 9000 requires “a long and steady breath” that meets “time, pressure, and slope requirements.” (BAOM, page 16). A person with a respiratory condition may produce a deficient or unacceptable sample not because they are impaired but because they cannot physically deliver what the machine demands. Diabetes and ketoacidosis can also produce acetone on the breath. The Intoxilyzer 9000 monitors multiple wavelengths to distinguish ethanol from other organic molecules, and an interferent detection should catch this. (BAOM, page 16). This is worth raising because it shows that the machine is testing for a specific chemical and that other chemicals can complicate the analysis. Whether or not your client was ever asked about any of these conditions can help discredit the accuracy and reliability of the breath test result. A documented condition from a medical professional can also help cast doubt on the machine’s results. The breath test operator manual, however, does not require medical screening the way the field sobriety test manual at least attempts to. The operator runs the test.
Machine Messages — A Catalog of Reasonable Doubt The Intoxilyzer 9000 generates specific messages when something goes wrong, and each message has a cause that may have nothing to do with intoxication. For a “complete test,” five things must be true: all air blanks must read 0.000; the two subject results must agree within 0.020; both calibration verifications must fall within 0.080 ± 0.010; the reference sample solution temperature must be within 34.00 ± 0.20 degrees Celsius; and “Test Complete” must print in the sequence box. (BAOM, page 13). If any of those elements is missing, the test is not complete by the machine’s own standards. When something goes wrong, the machine tells you why. Interferent Detected — the machine identified an infrared energy absorption pattern not specific for ethanol. (BAOM, page 16). In plain English, the machine detected something that was not alcohol. The manual says the operator should not attempt another breath test and recommends collecting a blood sample instead. If the officer got this message and ran another test anyway, they contradicted the machine’s own protocol. A blood test would have been the best available evidence. No 0.020 Agreement — the two breath samples differed by more than 0.020. (BAOM, page 16). This message could indicate residual mouth alcohol contamination, a rising or falling BAC, or instrument inconsistency. Whatever the cause, the machine itself is saying the two results do not agree well enough for the result to be considered reliable. Deficient Sample — three minutes elapsed without an adequate breath sample. (BAOM, page 16). This could be a result of impairment, respiratory problems, anxiety, or simply a subject not understanding the instructions. Whatever the case, the machine does not know why. It only knows it did not get what it needed.
Unacceptable Sample — this is caused by “an unacceptable change in the breath alcohol concentration” during delivery. (BAOM, page 16). The machine requires a long, steady breath. If the concentration changed during delivery, something interrupted the sample's consistency. Ambient Failure — this message results when the air blank was not 0.000, meaning something in the environment may be affecting results. (BAOM, page 15). This has nothing to do with the subject. Radio Frequency Detected — this message is the result of radio frequency energy above the threshold. Within the breath testing room, there are multiple causes for radio frequency energy, including two-way radios, cell phones, body-worn cameras, and microphones. (BAOM, page 15). Again, this is an error that has nothing to do with the subject, and oftentimes the officers standing near the machine with their body-worn cameras and radios can cause this. Totality of the Circumstances The manual uses this phrase - use it back. The totality of the circumstances isn't a DWI practitioner's invention. It's the manual's own language, and it's used repeatedly. In fact, the instructor manual tells officers to consider "the totality of all factors," including age, weight, environmental factors, location, injury, and physical ailments, when administering the walk and turn test (instructor manual, session 8, page 51). In the OLS stand (instructor manual, session 8, page 61), it tells officers that arrest decisions should be based on the totality of the circumstances (instructor manual, session 11, page 30). This matters because the state will try to isolate each test as independent evidence of intoxication. Your job is to do what the manual itself says the officer should have done—
consider all of it. When all of it includes deviations from the protocol, environmental factors, physical limitations the officer never asked about, clue definitions the officer did not follow, then the totality of the circumstances does not look like proof beyond a reasonable doubt. A Stranger’s Normal The arresting officer hopefully met your client for the first time on the side of the road. They do not have a baseline for your client. They do not know what your client's normal looks like. They don't know whether your client has a limp, a bad knee, a surgically repaired ankle, anxiety, an inner ear condition, nystagmus from a medical condition, or whether they've ever been able to stand on one leg for 30 seconds on a good day with no one watching. They don't know how your client walks. They don't know how your client talks. While the manual tells officers to ask about physical problems and disabilities before administering the psycho-physical tests, sometimes that is not enough. Asking these questions is not the same as understanding how a certain condition affects the client. Even an officer who checks every box and asks every question is still deciding about a stranger on the roadside with zero context about what this person looks like normally. Abnormal appearance does not necessarily equate to impairment, and an officer has no way of knowing this. Environmental Conditions Typical DWI investigation doesn't occur in a well-lit, flat-surfaced, dry area all the time. Typically occurs on roadsides at night, with lights flashing and traffic passing by. The manual acknowledges that this is a potential cause of a subject's poor performance
or clues that can be caused by things unrelated to intoxication. Sometimes when a subject is nervous, tired, scared, or standing in shoes that were not designed for roadside balance tests, these can also be reasons why someone does not perform well. An officer is asking a stranger to perform precise movements in an imprecise condition, conditions that the manual itself says may compromise the test. Every one of these conditions should be documented in every single case. Visit the scene. Photograph the surface. Look at its lighting and its proximity to traffic. If the officer's body-worn camera shows these conditions, then use it. If the officer's report doesn't mention those conditions, well, that's a gap. One that can be exposed through cross-examination because the manual tells officers that environmental factors matter and they simply chose not to document them. Using video, everything, for better or for worse, is on camera. Body-worn camera is simultaneously our best friend and sometimes our biggest challenge. It's our best friend because it catches every deviation, every rushed pass on HGN, every missed instruction on walk and turn, and every short or long OLS stand test. It's a challenge because juries will watch the video and form their own impressions regardless of what you argue about the clue definitions. The key is to highlight for the jury the deviations from what officers are taught: a frozen moment in time where an officer scored a clue that does not match the manual's definition. It is one thing to cross-examine the officer on the requirements and it's another thing to demonstrate to the jury the proper administration and the officer's deviation from that on his own body-worn camera. Sometimes what the video doesn't show can also be important. If the camera angle doesn’t capture a subject’s feet during the walk and turn test, the officer’s testimony about
heel-to-toe gaps is uncorroborated. The same applies if the camera doesn’t capture a subject’s eyes during the HGN test—those observations are unverifiable. The absence of the video corroboration does not mean the officer is wrong or lying, but it means that the jury must be asked whether, given everything, the officer's testimony is credible. The totality of the circumstances is not just the officer's observation, but it's also the conditions under which those observations were made. The limitations that the manual acknowledges and the deviations the officers may not realize that they had committed. Conclusion The DWI practitioner must know every clue on every test: all six clues on the HGN, all eight on the walk and turn, all four on the OLS stand. This is not just about the names of these clues but the precise definitions, the measurement thresholds, and the qualifiers the manual builds in. If you do not know that slight tremors should not be interpreted as swaying or that arms must move six inches or more, you'll miss an officer's deviation when it's sitting right in front of you on video. The manual tells officers to keep field notes because evidence of a DWI violation is short-lived, and those notes "could be useful if the officer is required to provide oral testimony." (Session 11, page 9). If the officer can use notes to refresh their memory, you can use a checklist to guide your cross-examination. DWI arrests are based upon an officer's subjective determination that your client was not normal. They have met a stranger for the first time under imperfect conditions, and it is their opinion, without any objective criteria, that landed your client in handcuffs. Our job is to hold those same officers to objective criteria that they were trained on in the
NHTSA manual. Every clue has a definition, and every test has a protocol. Every deviation has a consequence. The manual is their authority. Make it yours. That's the judo move.
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