M. Bonner Denton Strives to Improve the Quality of Forensic Science

For years, M. Bonner Denton, a professor of analytical chemistry and geosciences at the University of Arizona, has been developing a wide variety of analytical instrumentation for revolutionary analysis of trace chemicals. Much of this technology has found its way into the modern forensic laboratory.

Unfortunately, despite the fact that the instrumentation is exceptionally sensitive, the results can be presented in court testimony supporting hypotheses that are not justified scientifically. Bonner contends that when an individual with the title of “forensic scientist” takes the stand, the general public comprising the jury believes their testimony, even though their testimony can and sometimes does represent conclusions which cannot be based on the original scientific method. Worse, there are scientific methods practiced by some laboratories that have never been statistically validated nor their fundamental underpinning “science” proven. This can have dramatic consequences for plaintiffs and defendants. into both the capabilities and the limitations of a given analytical technique. A prime example of this is Bonner’s revolutionizing atomic spectroscopic emission analysis, which is employed today to analyze a wide range of elemental species. Denton’s expertise and his critical scientific mind have been recognized by his appointment to committees at the National Academy of Sciences which have resulted in two monographs, “Forensic Analysis: Weighing Bullet Lead Evidence” and the widely acclaimed and award-winning text entitled “Strengthening Forensic Science in the United States: A Path Forward” as well as serving on the National Commission on Forensic Science. This commission was a joint effort by the Department of Justice and the National Institute of Standards and Technology which reviewed the practices in forensic science, with the goal of ensuring that forensic science presented as evidence in the courtroom is scientifically and statistically sound.

Along with other respected experts in the field of forensics, Bonner has been a signatory on a number of amicus briefs filed with state supreme courts. These have resulted in the release of multiple individuals serving life sentences due to faulty or inconclusive forensic evidence, which in turn led to unjust convictions. As an example, Bonner has been a friend

By Hannah Schmidt

Photos courtesy of M. Bonner Denton

of the court in multiple cases contesting testimony involving “Bite Mark” identification with “forensic odontology.” Testimony in this arena has revolved around the claim that a given bite mark was from the defendant, but lately such claims often have been proven wrong. In one such case, the DNA evidence later demonstrated the bite was from a dog, and in another, the so-called “expert” recanted his testimony thirty years later saying that the marks on the victim were probably caused by the sharp prongs of a hurricane fence on which the victim was found. Convictions based on such testimony are deplorable, and such “evidence” should not be admissible. Bonner has served on the organizational committee for The Bitemark Thinkshop sponsored by the National Institute of Standards and Technology, in an effort to prevent this type of testimony from ever reaching a jury. This meeting brought together experts in forensic science, dentistry, judges, and other legal scholars.

Bonner contends that sometimes all that is needed is common sense and a modicum of scientific training. In a bombing trial held in Colorado, a forensics scientist had testified that the “tool marks” left on a tiny wire by a pair of wire cutters found in the possesson of the defendant “were without question the tool used to cut a wire found at the bombing scene.” In other words, his testimony assured the jury that no other wire cutters in the entire world could have cut the wire. Bonner strongly disputed this claim. While the “expert” might be correct in saying the marks are consistent with the tool in question, how could the “expert” possibly know that another pair or countless pairs of wire cutters did not exist somewhere in the world that could have made the same marks?

While Bonner sometimes calls on his scientific background, all too often he is simply providing plain old common sense, a talent that he uses to great effect in his work with organizations such as the Innocence Project or the Department of Justice.

AN INTERVIEW WITH BONNER DENTON

CBC Associate Professor Michael Marty sat down with Bonner Denton to ask about his career in chemistry.

MM: How did you get started in analytical chemistry?

BD: When I was 11 years old, I received my ham radio license and wanted to learn more, so I went down to an electronics company that wasn’t too far from my home. I told the owner I wanted to learn electronics and would work for free. He said ok and gave me a broom, so every day after school I swept the floor. I started to take things apart and troubleshoot it and often do repairs. I was too young to get paid, but I asked him to set up an account to let me buy equipment from the store. Later, I ended up working at a big wholesale electronics supplier in East Texas and repairing motel TVs.

When I was a freshman at Lamar University in Beaumont, Texas, I discovered that the chemistry department professors used quite a bit of electronics and instrumentation in their research, but they didn’t know how to repair it. Instantly, I had a job doing repair work and ended up as the teaching assistant for Instrumental Analysis. I said, you know, there is a niche here for my background in electronics, and since I enjoyed chemistry, I went to graduate school at the University of Illinois to study chemical instrumentation with Howard Malmstadt. While I was there, I did the first tunable laser excited atomic fluorescence spectroscopy. I came directly here as a new assistant professor, and the rest is history.

MM: What have you worked on at the University of Arizona?

BD: Over the years, we have revolutionized optical spectroscopy through development of array detectors. At the time when CCD and CID detectors were first coming out, people said it could not be done, but we designed the optics and figured out how to fabricate the difficult components. And now, every inductively coupled plasma optical emission instrument sold in the world uses array detector technology.

I also used my experience building ham radio gear to work with quadrupole mass spectrometers. We later built ion mobility devices to detect explosives, which led us into Homeland Security work. We are combining these now and developing cycloidal mass spectrometers with array detectors.

MM: How did you get into forensic science?

BD: I got involved in forensic science because every modern optical emission instrument used to identify trace levels of metals is directly traceable to the detection technology we developed. The FBI was using this technique to measure the elemental composition of lead projectiles and trace bullets found in the victim with a box of cartridges found in the possession of the defendant. I said, “Wait a minute, you can’t say that.” A few years later, when the National Academy was asked to take a look at the state of forensic science, I walked into this thinking forensic science probably had some rough edges but was pretty good. Now, I’m not convinced there’s a great deal of science in certain aspects of it. My role in this is that I want to put real science back into the field.

Read Prof. Denton’s monographs: bit.ly/BulletLead bit.ly/3F3xa9R