Bloodstain pattern analysis

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Bloodstain Pattern Analysis (BPA) is the study and analysis of bloodstains at a known or suspected crime scene with the purpose of drawing conclusions about the nature, timing and other details of the crime.[1] It is one of the several specialties of forensic science.[2]

The use of bloodstains as evidence is not new. However, since the late 1950s, BPA experts have claimed to be able to use biology, physics (fluid dynamics), and mathematical calculations to reconstruct with accuracy events at a crime scene and these claims have been accepted by the justice system. For example, the shape of blood droplets might be used to draw conclusions as to how far away the victim was from a gun when they were shot.

This technique of forensic science has drawn more skeptical scrutiny since 2000;[3][4] as part of the work in BPA was performed rather intuitively. A research report submitted to the U.S. Department of Justice by the National Academy of Sciences in 2009 highlighted several incidents of blood spatter analysts to overstate their qualifications as well as questioned the reliability of their methods.[5][6]


Early history[edit]

Bloodstain pattern analysis has been used informally for centuries, but the first modern study of blood stains was in 1895. Dr. Eduard Piotrowski of the University of Kraków published a paper titled "On the formation, form, direction, and spreading of blood stains after blunt trauma to the head."[7][8] A number of publications describing various aspects of blood stains were published, but his publication did not lead to a systematic analysis. LeMoyne Snyder's widely used book Homicide Investigation (first published in 1941 and updated occasionally through at least the 1970s) also briefly mentioned details that later bloodstain experts would expand upon (e.g., that blood dries at a relatively predictable rate; that arterial blood is a brighter red color than other blood; that bloodstains tend to fall in certain patterns based on the motion of an attacker and victim).[9] A 1952 episode of the police procedural radio series Dragnet made reference to bloodstain pattern analysis to reconstruct a shooting incident.[10]

Acceptance as valid evidence in United States courts[edit]

Between 1880 and 1957, courts in Michigan, Mississippi, Ohio, and California rejected expert testimony for bloodspatter analysis, generally holding that it added nothing to the jurors' own evaluations of bloodstains submitted as evidence.[4] In 1957, the California Supreme Court became the first American court to accept expert testimony examining bloodstains, accepting as evidence the testimony of Paul L. Kirk, a professor of biochemistry and criminalistics.[4] He would also testify in the Sam Sheppard case in 1966, when the wife of an osteopathic physician was beaten to death in her home, interpreting bloodspatter evidence as proof that the murderer was left-handed (Sheppard was right-handed).[4] However, bloodstain pattern analysis would not begin to enter wide use until it was promoted by Herbert Leon MacDonell. MacDonell researched bloodstains with a grant from the United States Department of Justice, and which also published his research in the book "Flight Characteristics and Stain Patterns of Human Blood" (1971).[4] MacDonell testified in court on multiple occasions as an expert of bloodstain analysis, and the legal precedent set by these cases led to its widespread use in American courts, although as early as 1980 some judges expressed strong doubts about its reliability, and it was not always accepted as evidence, especially in states with no prior rulings that relied on such evidence.[4]

The first formal bloodstain training course was given by MacDonell in 1973 in Jackson, Mississippi. MacDonell taught workshops on how to conduct bloodstain analysis, and the newly trained bloodstain analysts, who often had received as little as 40 hours of instruction, in turn would give expert testimony in court cases.[4] In 1983, the International Association of Bloodstain Pattern Analysts was founded by a group of blood stain analysts to help develop the emerging field of bloodstain pattern analysis.[8]

Further investigation into its admissibility as evidence[edit]

Starting in 1995, court cases where bloodstain analysts disagreed with each other raised concerns of the discipline's prediction's admissibility as evidence in court.[11][12][13] In 2009, the National Academy of Sciences published an examination of forensic methods used in United States courts which harshly criticized both bloodstain pattern analysis and the credentials of the majority of the analysts and experts in the field.[4][12] Judges have largely ignored the report's findings and continue to accept bloodstain pattern analysis as expert evidence.[4]

In 2013 Daniel Attinger, a fluid dynamics researcher at Columbia University, published a paper on bloodstain pattern analysis in Forensic Science International, finding that many of the central hypotheses of bloodstain analysis remain untested, and that existing analysts often made incorrect assumptions or other errors in their analyses. The paper also proposed fluid dynamics as a theoretical framework for solving these problems, and Attinger has continued to publish several papers exploring these concepts (as have other scientists as well). However, these papers are largely theoretical, and have had little impact on bloodstain analysis's use in courts.[4]


Bloodstain pattern analysis uses an analysis of the color, shape, and size of blood stains at a crime scene, as well as principles of fluid mechanics and biology to draw conclusions about the nature and proceedings of a crime scene. Particular attention is given to determining the angle of impact that caused a blood stain, in order to determine the blood's origin and the amount of force behind it.[14] Sometimes, software specifically designed to aid in bloodstain pattern analysis, such as HemoSpat, is used.

Bloodstain pattern analysis often uses extensive forensic photography in order to provide evidence for conclusions.


While bloodstain pattern analysis can be a useful tool for investigators the reliability of courtroom testimony by bloodstain pattern analysts has come under fire in recent years. Even with proper training and methods, there are still many times where reputable analysts disagree on their findings, which calls into question the reliability of their conclusions and its value as evidence in court.[6]

There is very little empirical evidence to support the use of blood spatter analysis in court or any other aspect of the legal system.[4] Like many other forms of forensic science, bloodstain analysis rests on the analyst interpreting ambiguity. This ambiguity can contribute to various forms of bias. For example, confirmation bias is the tendency to search for or interpret information in a way that confirms one's preconceptions or favored theory and to steer clear of the information that may disagree with those preconceptions. When an analyst has theories or preconceptions entering a crime scene, it may unintentionally influence how they interpret the blood stain. In addition, there are often no guidelines when they interpret a crime scene, and there often involves the use of discretion of the analyst. As an additional complication, not all blood is alike in humans; differences can make generalizing based on one experiment difficult. Because of these reasons, the validity of bloodstain analysis is likely not as high as many juries believe.

Relevant case histories[edit]

Warren Horinek[edit]

A 1995 murder case against Warren Horinek was largely decided based on bloodstain evidence that has been hotly disputed after the fact.[11] The case was bizarre in that the police and the district attorney's office believed in Horinek's innocence. The appointed attorneys for the prosecution found a bloodstain pattern analyst who testified that rather than a suicide - what the police believed was the case, due to a variety of reasons - it was a murder, because the pattern of small blood flecks on Horinek must have come from "high velocity" blood from a gunshot, rather than blood that got on him as he attempted to provide medical aid to the victim. Other bloodstain pattern analysts have since disputed this claim and said that the bloodstains were consistent with medical aid. The original analyst has walked back the strength of his claim somewhat, although he still believes in Horinek's guilt.[11] As of 2017, Horinek remains in prison.[15]

David Camm[edit]

In the criminal case against David Camm, who was tried three times for the murder of his family largely on the basis of blood spatter evidence, both prosecution and the defense used expert bloodstain pattern analysts to interpret the source of the approximately 8 drops of blood on his shirt. The prosecution's experts included Tom Bevel and Rod Englert, who testified that the stains were high-velocity impact spatter. Paul Kish, Barton Epstein, Paulette Sutton, Barrie Goetz, and Stuart H. James testified for the defense that the stains were transferred from his shirt brushing against his daughter's hair.[12] Dr. Robert Shaler, Founding Director of the Penn State Forensic Science Program, decried blood spatter analysis as unreliable in the Camm case. "The problem, in this case, is the number of stains are minimal," he said. "I think you're really on the edge of reliability." All of the blood spatter analysts involved in the case are "experts" in the traditional sense. The problem is "We have two opinions in this case. That, in essence, is a 50 percent error rate." An unacceptable level of reliability in a court case when the perception of guilt beyond a reasonable doubt is what is required.[16]

Further complicating matters was the testimony of Rob Stites. Stites testified for the prosecution that he was expert blood spatter analyst. It was later uncovered that he had no training and his credentials were fabrications by the prosecutor. His testimony that the blood on Camm's shirt was high-velocity impact spatter aided in the conviction of David Camm. Dr. Shaler pointed out that one limitation of blood spatter analysis testimony is that "you do not have the supporting underlying science" to back up your conclusions. When Stites testified, the jury had no way of knowing that he was not the expert that he purported to be. Even among the expert witnesses, it is unknown which set of experts interpreted the stains accurately as there is no objective way of determining which bloodstain pattern analyst has applied the science correctly.[17]

Travis Stay[edit]

Other times, bloodstain patterns from different causes can mimic each other. In the 2008 trial of Travis Stay for the murder of Joel Lovelien, prosecution witness Terry Laber testified that the blood spatter on Stay's clothing came from blows to Lovelien during a fist fight. After a review of the evidence by Paul Kish, another bloodstain pattern analyst, Laber reviewed the report submitted by Kish and revised his findings to include the possibility that the blood came from expiration by Lovelien.[13]

2016 Texas legal review[edit]

In 2016, the Texas Forensic Science Commission reviewed cases that had used bloodstain pattern analysis, and consequently established that starting in 2019, bloodstain pattern analysts will need accreditation to testify as experts in Texas courts.[4]

In popular culture[edit]


  1. ^ A Simplified Guide To Bloodstain Pattern Analysis, The National Forensic Science Technology Center (NFSTC), Florida International University
  2. ^ Bloodstain Pattern Analysis, Bureau of Criminal Apprehension, Minnesota Department of Public Safety
  3. ^ Adam Janos. How Bloodstain Pattern Analysis Works and Why It's So Controversial, A&E Television Networks
  4. ^ a b c d e f g h i j k l Smith, Leora (13 December 2018). "How a Dubious Forensic Science Spread Like a Virus". ProPublica. Retrieved 19 December 2018.
  5. ^ National Research Council. Strengthening Forensic Science in the United States: A Path Forward. Washington, DC: The National Academies Press, 2009. Archived
  6. ^ a b Moore, Solomon (February 4, 2009). "Science found wanting in nation's crime labs". New York Times.
  7. ^ Eduard Piotrowski, Ueber Entstehung, Form, Richtung und Ausbreitung der Blutspuren nach Hiebwunden des Kopfes [On the formation, form, direction, and spreading of blood stains after blunt trauma to the head] (Vienna, Austria: 1895).
  8. ^ a b Brodbeck, Silke (2012). "Introduction to bloodstain pattern analysis" (PDF). Journal for Police Science and Practice. 2: 51–57. doi:10.7396/IE_2012_E.
  9. ^ Snyder, LeMoyne (1971). Homicide Investigation: Practical Information for Coroners, Police Officers, and Other Investigators. Charles C. Thompson Publishers, 3rd Edition
  10. ^ "Judging from the bloodstains found on the furniture and rug in the living room, and on the front steps of the cottage, Radford had been first been shot while he was in the living room..." Quote starts at about 12 minutes and 17 seconds into the episode. "The Big Streetcar", April 3, 1952; no script writer identified.
  11. ^ a b c A Bloody Injustice
  12. ^ a b c Kozarovich, Lisa Hurt. "Blood Spatter Evidence Not an exact Science". News and Tribune. Retrieved 8 February 2014.
  13. ^ a b Archie Ingersoll. Travis Stay found not guilty, Grand Forks Herald, December 17, 2008
  14. ^ Stuart H. James, Paul E. Kish, T. Paulette Sutton (2005). Principles of Bloodstain Pattern Analysis: Theory and Practice. Boca Raton, FL: CRC ISBN 9780849320149
  15. ^ Bloody Injustice - The Warren Horinek Case
  16. ^ Kircher, Travis. "David Camm blogsite: Our own little experiment". WDRB. Retrieved January 1, 2014.
  17. ^ Kircher, Travis. "David Camm blogsite: Uncle Sam". WDRB. Retrieved January 1, 2014.

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