Sophia Tang
Senior Thesis | 2025
The Comparative Study on Variation in Blood Drip Stains
Characteristics due to Change in Paper Varieties
Sophia Tang
Abstract:
Even with the widespread use of technology, paper is still widely distributed across the world in many forms such as folders, notebook paper, books, and more. This study investigates the drip stain formation on 13 different paper varieties and examines the effects of roughness, porosity, thickness, absorbency, and fibre content and structure. A total of 39 drip stains were collected from droplets created perpendicular to the surface, with three rounds for each paper variety on the same dripping height. Digital images were photographed using a 39 Canon DSLR. The droplets created in this study exhibited consistent differences between papers of different textures, porosities, absorbencies, and thickness.
Introduction
Crimes can happen in any environment, and as a common factor among many crime scenes, bloodstains are studied by many studies. Bloodstain pattern analysis (BPA) is a field of forensic science that is the collection, categorization and interpretation of the shape and distribution of bloodstains associated with crimes involving bloodshed. The analysis of these bloodstain patterns will contribute information about the distance from the target, its angle of impact, direction of travel, nature of external forces and objects used to cause bloodshed, and result in the interpretation of the crime that led to the bloodshed (10). The aim of the bloodstain pattern analyst is to gather information from the bloodstain’s data
through its physical characteristics before identifying and tracing the pattern back to a source event within the context of the scene to find key clues to possibly locate and identify the culprit. An example of this applying in real life is using the physical characteristics of a dried drip stain to estimate the blood source, relying on both the characteristics of the dried stain and specific fluid properties of the blood droplet during flight to estimate dripping height (7). This would greatly contribute to the restoration of the crime scene for the purpose of finding the culprit.
However, despite the importance of this field, BPA lacks a solid framework, and its procedures are often based on the situation, which is understandable when looking at the wide variety of crimes committed yearly. However, its results rely less on numerical opinions and more on reasoning and logical processes succeeding the evidence collected (1). For the purpose of strengthening their understanding of bloodstain, and in order to be able to acquire better, more reliable data, many studies have looked into the interactions between bloodstains and the environment around them. Perhaps because of the larger focus on drip stains on textiles or other solid materials, the dynamics between blood and paper is overlooked, even with paper’s ubiquity across schools, homes, libraries, and offices. This study aims to fill in that gap, investigating the formation of blood drip stains on 13 different but similar paper types, ranging from paper towels to papyrus.
Bloodstain Types
To understand the bloodstains that an examiner might be presented with, they need to be able to investigate these stains and understand the process of their formation. A bloodstain pattern is a physical, geometric image created by blood contacting a
surface, an example being figure 1.1. Passive bloodstains are created by gravity and can be categorized in three separate variations. Passive stains include drops, flows and pools, and typically result from gravity acting on the blood originating from a body with an open wound. Transfer stains result from objects coming into contact with existing bloodstains and leaving wipes, swipes, or pattern transfers behind such as a bloody hand print or a smear from a body being dragged. This includes altered stains blood patterns that have gone through physical or physiologic alterations. Examples include clotting, dilution, drying, diffusion, insect activity, sequences, and void interference. Impact stains result from blood projecting through the air and are usually seen as spatter, but may also include gushes, splashes and arterial spurts. These splatter stains exhibit directionality, vary in size, and are created as a result of external forces including gravity and friction. They are caused by impact mechanisms, secondary mechanisms, and projection mechanisms.
Formation
The shape of bloodstains is influenced by factors such as the angle of impact, speed, distance, and surface texture. The texture of the surface plays a significant role in determining the stain’s shape, size, and location. Hard, non-porous surfaces often produce smaller stains with well-defined edges, while porous surfaces absorb more blood, leading to larger, diffused patterns. (2). The direction of travel can be deduced from the pointed end of the bloodstain, which always faces its direction of movement. By analyzing the distance between the point of origin and the point of convergence, as well as the angle of impact, investigators can reconstruct the blood's point of origin. This process can be enhanced using the tangent method (Tangent of Angle = Opposite/Adjacent or Z/Y) to calculate the point of origin
precisely (3). The site of origin refers to the location where the blood that formed the stain originated, providing critical insight into the events that occurred (3).
Viscosity and cohesion between cells also play their part in how blood behaves outside the body. When met with external forces, blood behaves differently from water due to its properties and it behaves like a non Newtonian fluid. As a non Newtonian fluid has no constant viscosity and depends on the amount of stress applied to it, it is necessary to investigate bloodstain formations as BPA is heavily related to fluid dynamics (9), and while water can be used as a comparison point, assuming that blood’s formations are the same as water formations would lead to inaccurate conclusions. When the blood falls from the source, the circular droplet essentially splashes out of itself to create the different patterns that are visible to the human eye. There are four phases of impact: contact and collapse, displacement, dispersion, and retraction. Contact and collapse is when the droplet comes in contact with a surface, it begins to collapse within itself. The top part of the droplet remains intact, and most of the blood is pushed outward, forming a ring. Displacement is how after the droplet has finished collapsing, the remaining blood that did not form the rim is pushed out, which forms an irregular edge on the droplet. However, the surface tension is not yet broken on the droplet so it remains as one entity. Dispersion then happens; the blood that is pushed outward breaches the rim and forms the patterns that are easily recognizable. These include crowns and other slight abnormalities. With more acute angles of impact, the patterns that form are forced out on one side of the droplet, causing the patterns to only appear on the opposite side of impact. Retraction finally occurs as the surface tension of the droplet is broken and tails, spines, and satellites are formed (4).
Surfaces
Investigators primarily focus on angles, surfaces, and patterns when conducting bloodstain analysis. These elements help reconstruct the scenario of the incident and provide clues about how the blood was shed. In bloodstain pattern analysis, it is important to know the effect of different surfaces on the shape and size of the bloodstain as this will affect the bloodstain’s appearance and the investigating team’s analysis and recreation of the scene. Surface textures play a vital role in influencing these bloodstain patterns. In a study on strictly non-porous surfaces, the surface roughness was found to not only influence the splashing limit but also heavily impact the smoothness of the edge of the parent stain, and the researchers concluded that roughness and velocity were the two main parameters controlling the post impact pattern of blood (5).
A significant goal of this study is to gather data on common bloodstain patterns across various paper types. Understanding these patterns aids in standardizing interpretations and improving analysis reliability. Expected outcomes include a combination of different passive blood drip stain types. More porous materials are predicted to absorb more blood, resulting in a larger source area, while less porous surfaces are likely to create stains with smaller surface areas. These findings can refine the interpretation of bloodstain evidence in forensic contexts.
Methods
To test our hypothesis, we conducted an experiment set up using 13 different types of paper, with each being subject to three rounds of drip stains using a dropper. For the creation of drip stains, both a pipette and a dropper could be used. However, while the volume of uL coming from a pipette is consistent, droplets
from a pipette would be difficult to extract. On the other hand, droplets are easily pushed out from a dropper, but a dropper has no determined accuracy for the droplet volume. To verify the accuracy and reproductivity of using a dropper, a test round using a dropper was conducted, and 100 rounds of water droplets were measured with a 100 ml pipette. Measurements varied between 43 - 48 ml, with 45 ml having the highest frequency of occurring 50 times, leading to the conclusion that a dropper was a viable choice for the experiment.
For the actual experiment, bovine blood is dropped from a 37.5 in lab countertop height to 13 different swatches of paper
Table 1: Test drop results (with water)
commonly found in places crime scenes would happen in, specifically in schools, bathrooms, studies where paper mediums are ubiquitous. Pictures were taken with a Canon DSLR mounted on a 3 legged tripod to accurately measure the source area at home. Blood drip stains were measured with a 8 x 8 cm measuring tape.
Results
For item 1, cardboard, the source area produced a circular and collected stain, with long thin spines. Longer spines are observed stretching into satellite stains, mostly evenly spaced around the circle. The perimeters of the stains are mostly scalloped, with a mostly consistent distance between the distinct scallops and spines. Item 1c has an edge slightly more scalloped towards the upper right corner. These stains include an uneven distribution of blood, as item 1a and 1b displays a noticeable bump in the middle, with lighter colors of blood seen throughout all three test rounds, indicating how there is less blood in that particular area.
1a, 1b, 1c
Figure.
Item 2, the paper bag, was made of similar material to item 1, giving it a similar surface texture to item 2, resulting in a similar appearance to item 1’s stain an even shape and evenly spaced satellite drops. However, as the paper bag lacks the scaffolding between the cardboard’s sheets, it has less structure, and small pooling on its surface can be seen. Compared to item 1, item 2 lacks thickness and the blood’s uneven distribution is more prominently displayed. The bloodstains here display evenly spaced, flattened scalloped edges, with shorter and thicker satellite drops compared to item 1.
Figure. 2a, 2b, 2c Item 3, white cardboard, has an area with short and wide spines, with a less balanced shape shown by the unequal areas of margins in between the scallops and spines, and numerous smaller satellite drops. Satellite stains are spread mostly evenly around the perimeter with the exception of avoiding the more obviously scalloped areas. With the exception of item 3b, the blood can be evenly distributed throughout the blood drip stain, and less pooling can be seen, though blood clumps can still be seen if observed carefully in item 3b and 3c. Item 3 overall has a more scalloped edge, as seen in item 3b and 3c, with item 3b having a scalloped edge towards the upper left and item 3c having a scalloped edge facing the bottom left.
3a, 3b, 3c For item 4, watercolor paper, its area is even, with an overall circular shape, and evenly distributed spines like waves with occasional longer, thinner spines dispersed evenly around the perimeter. The blood in the source area is well balanced, with no noticeable blood clots forming in the origin source after drying. However, a grainy texture is still observed after drying. Around the perimeter, the spines and scallops have an even and mostly consistent distance between each other.
4a, 4b, 4c For item 5, charcoal paper, the stain is mostly circular, with medium to small spines which are closely spaced from each other in a consistent fashion. The medium can be seen visibly crumpling up in certain areas of the stain, creating oval-like, dried
Figure.
Figure.
up pools of blood in the middle of the stain. From item 4b and 4c, it can be seen that spines and satellite stains tend to grow longer if perpendicular or directly connected to the small pool of blood. The texture after drying shows that pools of blood are smooth, while the areas with less blood resemble the original paper’s texture.
Figure. 5a, 5b, 5c
Item 6, an office folder, has widely spaced short spines, with smaller margin distances observed between the shorter scallops around the perimeter, and an even, circular shape. The surrounding satellite stains tend towards to be thin but numerous, as demonstrated most prominently in item 6c. The blood distribution can be seen as even, with items 6a and 6b demonstrating the blood gathering in the middle, while item 6c shows the blood gathering around the edges of the stain. However, the subtle pooling does not occur in a circle, instead, it is shown in an oval like manner in items 6a and 6b, while acting in a parallel display on the top and bottom of item 6c. Where the blood can be identified as more frequent, the texture is grooved and bumpy, whereas the texture is smoother on the areas with less blood.
Figure. 6a, 6b, 6c
Item 7, the glossy side of a calendar, has an even shape with no satellite stains, and short scallops which are also widely spaced around the edges. The stains mainly consist of low scallops and the distance between these scallops are consistently wide. The surface of the medium is even when dried but slightly puffed up when wet. The dried texture is smooth.
Figure. 7a, 7b, 7c
Item 8, printer paper, has an even shape but slightly irregular spines that range from short to medium length, with little to none satellite stains. Any found satellite stains are small dots. The uneven distribution of blood is similar to the blood distribution in item 1. As the medium dries, the areas where more blood can be seen are observed to rise up or down in the shape of wrinkles. Near the wrinkles, scallops sometimes combine or
distort into a wider shape, as most seen in item 8b. The other two, items 8a and 8c, mostly show short spines with a close and consistent distribution of margins between them. However, near the lighter regions of the bloodstain, the edges can be observed distorting, with examples being the scallops flattening, expanding, or having the distance between two scallops widening.
Figure. 8a, 8b, 8c
Item 9, notebook paper, has slightly irregular spines that range from short to long. Its spines are mostly short and closely spaced together. The medium, like item 5, exhibits wrinkling in parallel lines. Darker areas of blood can be seen pooling horizontally parallel to each other. However, in contrast to item 5, the paper can also be observed crumpling up at the edges of the stains, and some of the wrinkles inside the blood stain can be seen extending beyond the bloodstain onto the blank paper. Near the pools of blood, satellite stains are shortened, and more distortion of the scallops can be seen.
9a, 9b, 9c
Item 10, papyrus paper, has an irregular shaped circle with random spines that range from short to long. Spacing from spines are all irregular and the satellite stains are long and thin or spotlike, extending ubiquitously in all directions. Item 10a has an extremely scalloped edge. There is no wrinkling, but there is an uneven distribution of blood. All three rounds have noticeable air bubbles inside the stain and the texture is bumpy.
10a, 10b, 10c
Item 11, textbook paper, has mostly short spines closely put together, with occasional thinner spines that sometimes extend to long, thin satellite stains. All three rounds have wrinkles around the perimeters, and some parts of the origin stain can be seen connecting to larger wrinkles. Unlike items 9 and 5, the wrinkles
Figure.
Figure.
are not in a linear manner, instead, curving in an oval shape like in item 11a, or stretching irregularly like in item 11c. The blood is clearly blotchy in the lighter areas, and the perimeter shows smaller spikes going around the larger scallops and spines.
11a, 11b, 11c Item 12, quilted paper towels, has a small irregular shape, with large amounts of circular satellite stains. There are no elongated satellite stains, and none of the stains have definitive scallops or spines due to the absorbency of the material. The surface texture still shows a large visual resemblance to the unstained medium, with the only difference being harder to the touch. There is no wrinkling nor pooling, and the blood is distributed evenly.
12a, 12b, 12c
Figure.
Figure.
Item 13, smooth paper towels, has irregularly shaped spines, with a singular round satellite stain in items 13a and 13b. The stains have no distinct scallops or spines. Light wrinkles can be seen forming around the perimeter of the stains, but the middle of the stains remain even. Like item 12, the surface texture shows a visual resemblance to the unstained medium, with the only difference being harder to the touch, and the blood is distributed evenly.
Figure. 13a, 13b, 13c
The size, shape, and distribution of the bloodstains on each surface was determined by eye. The average diameter of bloodstains ranges from approximately 1.9 to 3.1 cm. With items 10, 12, and 13 giving the highest diameters and items 7 and 6 giving the lowest diameters. Overall, items 7, 11, 1, and 6, have even shapes, relatively little satellite stains, and small, wide spines. Items 13, 12, and 10 have irregular shapes and spines. Meanwhile, the rest of the items have even shapes and occasional irregular spines. Item 13, a paper towel who is both rough and porous in texture, is one of the largest stains, the capillary motion
of blood giving it a wider movement range due to the quilted paper towel’s properties and its roughness also increasing its size. Item 10, as the second largest stains, had a larger stain due to its surface roughness but had less area compared to the more porous item 13. Local variations in surface roughness of the paper were responsible for introducing some randomness in the size of spines and also led to some merging of spines. When a drop of blood hits a hard or non- porous surface, such as item 7, glossy calendar paper, it results in fewer spatters and a more cohesive circle. If the drop hits a rougher surface such as item 10, papyrus, it will result in an irregular shaped stain that has serrated edges and more satellite spatter around it.
Figure 14. Blood drip stain diameter for items 1 to 13, including each of the three rounds labeled a, b, and c respectively.
Table 2: Measurements of the drip stains with each blood drip stain round.
10 Papyrus
11 Textbook
Discussion
Different types of bloodstain patterns seen when the drop of blood strikes the surface. The interpretation of bloodstains found on paper provides valuable information, which may assist in determining the facts surrounding a criminal case. Therefore, a systematic study was conducted to characterize the appearance of drip stains on a variety of different paper sources on a flat surface in order to develop a baseline for investigation into more complex interactions, such as bloodstains on inclined surfaces. The type of surface that a blood droplet strikes affects the amount of resultant stain distortion and satellite blood spatter, so consideration of surface texture is a key observation when determining the characteristics of the blood spatter.
A blood drop impacting a surface is subject to many variables including drop volume, velocity and impact angle. A previous study using different types of fabrics found that the widths of inclined bloodstains on fabrics would increase in size
depending on the wicking capabilities of the fabric being investigated. On the fabric, their drop was affected by variables such as fibre content, fabric structure, absorbency, surface roughness, thickness and porosity. The blood drop initially spreads over and within the fabric due to its inertial force at impact (wetting), and this may be followed by further movement of blood within the fabric which is dependent on fabric properties such as its wicking (8). The wicking capability is coined for when the fabric pulls moisture away from the skin using tiny, built-in capillaries which is somewhat similar to porosity in paper. This would explain the larger size difference(figure 14., table 2) and the number of satellite stains on items 5, 12 and 13, the charcoal paper and the two paper towel samples, as charcoal paper is made to have many smaller grooves in order to better facilitate the adheration of charcoal to the surface, while paper towels are made to pull moisture away from surfaces giving them high wicking capacities.
Additionally, both item 12 and 13, the paper towel types, have no distinct scallops or spines at their edges due to their high absorbency. These results match those of snow, found by a relevant study by Plante et al. (6). Bloodstains on snow showed that the bloodstains exhibited irregular characteristics compared to those seen in bloodstains on hard, non-porous and nonabsorbent surfaces created in ambient laboratory conditions like this study. The irregularity was likely due to the permeability of snow. Bloodstains continued to diffuse and spread through the surrounding snow after the splashing phase was completed, contributing to the irregular patterns observed (6). As paper towels have a high permeability due to their purpose for cleaning up, their source areas would resemble those of snow.
Items 1, 2, 8, and 11, cardboard, paper bag, print paper, and textbook paper respectively, all collectively display blotchy
areas in their area of convergence. This implies that they have a similar absorbency and surface roughness. Whenever a process involves the wetting of a solid by a liquid, three different interfacial boundary surfaces the boundary between two spatial regions occupied by different matter solid-liquid, solid-air, and liquid-air are involved. Wetting replaces an area of the solid-air interface by an equal area of solid-liquid interface (14). So when blood falls onto the paper, it fills in the unseen grooves in the paper, and when paper is saturated, the blood will gather in groups, forming the blotchy pattern in figures 1, 8, and 11.
Two outliers that significantly differ visually from the other mediums are items 10 and 7. Item 7, the calendar paper treated to show a glossy surface texture, is the opposite of item 10, as it differed from the other mediums due to its consistently circular shape with no elongated satellite stains or spines, with only wavy margins. This result matched with those of another study on variations in blood stains due to surface textures. Using a variety of animal blood to test the difference of the resultant stains on a range of surfaces, they observed that bloodstains resulted in less splatter on hard, nonporous surfaces such as tiles compared to rougher surfaces like wood (3). On a hard smooth surface there are least distortions in the shape of bloodstains (2). This can be attributed to the glossy paper and the nonporous surfaces having little to no grooves or pores for the blood spread resulting in its neat appearance.
When a drop of blood hits a hard or non- porous surface, such as glass or smooth tile squares, it results in fewer spatters. However, if the drop hits a rougher surface such as carpet or wood, it will usually result in an irregular shaped stain that has serrated edges and has satellite spatter around it as rough textured or porous surfaces will produce more distorted, irregular shapes (12). This is explained by the porous surface causing the drop to rupture as the forces of surface tension are overcome on impact.
This is demonstrated by item 10, as it displays a heavily irregular area of convergence with tiny air bubbles forming in the stain. Unlike the other paper mediums, item 10, papyrus, has a visually rougher texture, with its fibers visible to the naked human eye. From the tiny air bubbles, it can be inferred that papyrus has little to no permeability for the blood to seep through as even air bubbles can be trapped between the blood and the papyrus fibers.
Items 3, 4, 6, and 9, white cardboard, watercolor paper, folder paper, and notebook paper show a consistent pattern of parallel pooling, where instead of settling in a blotchy manner like items, 1, 2, 8, and 11, the blood dries in linear pools parallel to each other. Wrinkling inside the source area and around the perimeters is seen most prominently in this group of mediums. This demonstrates the absorbency and the thickness of these papers. When paper is immersed in water, the absorbed water disrupts and expands the paper fibers, causing wrinkling (14). Doing the same with blood would result in a similar result. The reason why these mediums show more prominent wrinkling compared to the other mediums is because their thickness is significantly thinner than the other mediums and these do not have other unique properties such as item 7, the glossed calendar paper, or item 5, the charcoal paper with more grooves. As a result, after the blood saturated the paper fibers, the remaining blood has nowhere else to spread causing blood pools. The parallel nature of these blood pools may be due to the paper’s wrinkling in lines, therefore causing the blood to pool linearly.
Limitations and Future Improvements
While bloodstain analysis can be highly informative, its reliability is not absolute. Error rates can occur due to subjective interpretations, environmental factors, or limitations in experimental replication (11). This study is also applicable to
these factors as it was conducted with a limited amount of technological resources and the finding of results may include human error due to the analysis of the bloodstains being done by hand. For future research, it is recommended to calculate the surface roughness of the paper, use pipette for precise blood volume, and use a wider variety of paper mediums. An example of a useful technology would be FIJI as demonstrated by another study where they determined the surface roughness by converting their bloodstain images to a RGB stack format in FIJI before using a Extended Depth of Field plugin to create a height map before processing with SurfCharJ plugin to obtain the arithmetic average roughness (Ra), which measures the average difference in height between peaks and valleys on a surface (6).
Conclusion
Bloodstain analysis is a critical tool in forensic investigations, as it helps determine the location of events, the time of occurrence, the types of weapons used, and the sequence of actions at a crime scene. By carefully analyzing bloodstain patterns, investigators can reconstruct the crime's narrative and provide essential evidence in solving cases. In this study, it was gathered from the present data that materials with higher porosity absorbed more blood, resulting in various different features such as larger diameters(item 5), wrinkling(items 3, 4, 6, 9), blotching(items 1, 2, 8, 11), or irregular edges(items 12, 13) due to their characteristics, while less porous surfaces created stains with with varying results each(items 10, 7). This indicates that the way in which blood interacts with these different surfaces is different, giving a need for further understanding of differences in the pattern of blood on different paper surfaces to supplement information for the better interpretation of bloodshed at crime
scenes. These findings can refine the interpretation of bloodstain evidence in forensic contexts by providing a reference and point of comparison for future studies. This study was a preliminary investigation to validate the diverse nature between paper and blood, indicating this direction needs further study.
Acknowledgements
We would like to express our gratitude to Dr. Amy Brodeur for her wonderful guidance and advice throughout the experiment and in the research paper and Victoria Perrone for her support and management during the process of writing this paper.
Bibliography
1. L. Meijrink; Scheer, M.; Bas Kokshoorn. Bloodstain Pattern Analysis & Bayes: A Case Report. Science & Justice 2023, 63 (4), 551–561. https://doi.org/10.1016/j.scijus.2023.06.005.
2. Dubey, M. K.; Sharma, R.; Patel, K. K. (PDF) A comparative study on variation in bloodstain patterns due to change in surface-using blood from four common animal species. ResearchGate.
https://www.researchgate.net/publication/336438318_A_co mparative_study_on_variatio n_in_bloodstain_patterns_due_to_change_in_surfaceusing_blood_from_four_common_ animal_species.
3. Sonia, R. Investigation of Stain Patterns from Diverse Blood Samples on Various Surfaces. Journal of Forensic Science and Research 2024, 8 (1), 028–034. https://doi.org/10.29328/journal.jfsr.1001061.
4. 6.01 Blood Spatter. accessdl.state.al.us. https://accessdl.state.al.us/AventaCourses/access_courses/ forensic_sci_ua_v17/06_unit/0 6-01/0601_learn_text.htm.
5. Smith, F. R.; Buntsma, N. C.; Brutin, D. Roughness Influence on Human Blood Drop Spreading and Splashing. Langmuir 2017, 34 (3), 1143–1150.
https://doi.org/10.1021/acs.langmuir.7b02718.
6. Plante, J.; Orr, A.; Albrecht, I.; Wyard, L.; Boyd, P.; Stotesbury, T. Drip Stains Formed on Ice and Snow: An Observational Study. Canadian Society of Forensic Science Journal 2021, 54 (2), 61–76. https://doi.org/10.1080/00085030.2021.1880726.
7. Stotesbury, T.; Taylor, M. C.; Jermy, M. C. Passive Drip Stain Formation Dynamics of Blood onto Hard Surfaces and Comparison with Simple Fluids for Blood Substitute Development and Assessment,. Journal of Forensic Sciences 2016, 62 (1), 74–82. https://doi.org/10.1111/1556-4029.13217.
8. de Castro, T. C.; Carr, D. J.; Taylor, M. C.; Kieser, J. A.; Duncan, W. Drip Bloodstain Appearance on Inclined Apparel Fabrics: Effect of Prior-Laundering, Fibre Content and Fabric Structure. Forensic Science International 2016, 266, 488–501. https://doi.org/10.1016/j.forsciint.2016.07.008.
9. Attinger, D.; Moore, C.; Donaldson, A.; Jafari, A.; Stone, H. A. Fluid Dynamics Topics in Bloodstain Pattern Analysis: Comparative Review and Research Opportunities. Forensic Science International 2013, 231 (1-3), 375–396. https://doi.org/10.1016/j.forsciint.2013.04.018.
10. James, S. H.; Paul Erwin Kish; T Paulette Sutton. Principles of Bloodstain Pattern Analysis : Theory and Practice; Crc: Boca Raton, Fla., 2005.
11. Hicklin, R. A.; Winer, K. R.; Kish, P. E.; Parks, C. L.; Chapman, W.; Dunagan, K.; Richetelli, N.; Epstein, E. G.; Ausdemore, M. A.; Busey, T. A. Accuracy and Reproducibility of Conclusions by Forensic Bloodstain Pattern Analysts. Forensic Science International 2021,
325 (325), 110856.
https://doi.org/10.1016/j.forsciint.2021.110856.
12. Saferstein R. Criminalistics: An Introduction to Forensic Science. 4th Ed. Upper Saddle River, N.J: Prentice Hall, 2001, 324-28.
13. Wenzel, R. N. RESISTANCE of SOLID SURFACES to WETTING by WATER. Industrial & Engineering Chemistry 1936, 28 (8), 988–994. https://doi.org/10.1021/ie50320a024.
14. Vitale, T. Effects of Water on the Mechanical Properties of Paper and Their Relationship to the Treatment of Paper. MRS Proceedings 1992, 267. https://doi.org/10.1557/proc-267-397.