Bloodstain pattern analysis

Bloodstain pattern analysis (BPA), one of several specialties in the field of forensic science, involves the study and analysis of bloodstains at a known or suspected violent crime scene with the goal of helping investigators draw conclusions about the nature, timing and other details of the crime.

The use of bloodstains as evidence is not new; however, the application of modern science has brought it to a higher level since the 1970s and '80s. New technologies, especially advances in DNA analysis, are available for detectives and criminologists to use in solving crimes and apprehending offenders.

The science of bloodstain pattern analysis applies scientific knowledge from other fields to solve practical problems. Bloodstain pattern analysis draws on the scientific disciplines of biology, chemistry, mathematics and physics. If an analyst follows a scientific process, this applied science can produce strong, solid evidence, making it an effective tool for investigators, although care does need to be taken when relying on bloodstain pattern analysis in criminal cases. A report released by The National Academy of Sciences calls for more standardization within the field. The report highlights the ability of blood spatter analysts to overstate their qualifications and the reliability of their methods in the court room.

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." 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).

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