Bloodstain Pattern Analysis
What is Bloodstain Pattern Analysis?
The textbooks will tell you Bloodstain Pattern Analysis, often abbreviated as BPA, is the analysis of the size, shape, distribution, and location of bloodstains and the patterns they create. In more common terms, it’s a way of examining blood present in crime scenes—on evidence, or even on victims, witnesses, or suspects—that helps us recreate events.
For example, back spatter on a suspect may indicate that he or she was present when a victim was shot. In the same way, spatter on the hands of a deceased suicide suspect may confirm or refute evidence of a suicide. These details, which may seem minor to the untrained eye, can carry enormous weight in determining what truly happened.
Making Order from Chaos
When the untrained investigator or lay person walks into a particularly bloody crime scene, they may see only “blood everywhere.” But to a trained analyst, every stain and every pattern has meaning. Analysts classify stains according to well-established definitions created by the International Association for Bloodstain Pattern Analysis (IABPA). These classifications are based on measurable characteristics such as size, shape, and distribution, and they are updated regularly to reflect current standards.
This system of classification allows analysts to separate chaos into categories, giving structure to what might initially appear overwhelming.
Is It a Real Science?
Often you may read, see, or hear that bloodstain pattern analysis is a pseudoscience—that it’s not real and has no basis in the world of science. This is a fallacy. Bloodstain pattern analysis is an applied science that relies on math, physics, biology, and chemistry. In essence, it is fluid dynamics, but involving one very specific fluid: blood.
This does not mean BPA is infallible. The failures generally come from the analyst’s inability to properly interpret the evidence, not from the science itself. Recognizing this distinction is critical.
Reducing Errors Through Peer Review
Over the years, BPA has adopted processes to help reduce inaccuracies in interpretations. One of the most important is the peer review system. Upon completing a bloodstain pattern analysis, the analyst seeks a second analyst to review the work. The review specifically looks for erroneous classifications or unsupported conclusions.
There are several recognized ways to perform peer reviews. One method is the blind peer review, in which the second analyst is not given the first analyst’s report, but only the original documentation. They must then reach their own conclusions independently.
The idea is simple: if two trained analysts look at the same material and reach the same conclusions, then there is a high likelihood those conclusions are correct. This process is crucial, because when an analyst misinterprets bloodstain evidence, the consequences can be dire.
The Case of David Camm
A frequently cited example of BPA’s so-called “failure” is the case of David Camm, a former Indiana state trooper wrongfully convicted of murdering his family. Critics sometimes use this case to argue that BPA is unreliable.
However, closer examination reveals the problem was not with the science but with the unqualified practitioner who claimed expertise in BPA. Camm had a strong alibi—he was playing basketball at the time of the murders—but prosecutors relied on flawed testimony and ignored exculpatory evidence. Highly qualified experts attempted to intervene, but their findings were dismissed.
The Camm case represents a tragic miscarriage of justice fueled by bias and misuse of forensic evidence, not a true failure of bloodstain pattern analysis itself. Such cases highlight the importance of proper training, established standards, and peer review within forensic science.
Why Bloodstain Pattern Analysis Is Useful
Blood is a non-Newtonian fluid, more specifically a pseudoplastic or shear-thinning fluid. It does not behave like water, but it does behave predictably under given conditions. By applying scientific principles to bloodstains, analysts can provide critical insights into what happened at a scene—whether identifying the position of a victim, determining the type of weapon used, or distinguishing between homicide and suicide.
When performed by a trained analyst and subjected to proper review, BPA remains a powerful tool in crime scene reconstruction and in the pursuit of justice.
Need Expert Bloodstain Pattern Analysis?
Bloodstain evidence can be the difference between clarity and confusion in a criminal investigation. When properly analyzed, it can strengthen cases, reveal overlooked details, and ensure the truth is presented in court. But when misinterpreted, it can lead to devastating errors.
At TriStar Forensic Consulting, we specialize in crime scene reconstruction, bloodstain pattern analysis, and shooting incident reconstruction and review. With years of law enforcement and forensic training experience, we provide the insight that attorneys, investigators, and agencies need to evaluate evidence with confidence.
Contact us today to have your case reviewed for accuracy.