Crime and Justice Atlas

How Justice Is Served
Forensic Disciplines and Methods

Bloodstain Pattern Analysis

Also Known As BPA

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The interpretation of bloodstains at a scene, using pattern recognition and the physics of droplet flight to reconstruct the events that produced them. Herbert Leon MacDonell formalized the field with his 1971 study of the flight characteristics of human blood and taught its first formal course in 1973, and its scientific standing has since been seriously challenged.

Facts
Disputed
Known Limitation
Following Daubert-standard admissibility challenges, courts have divided on whether bloodstain pattern analysis testimony meets reliability requirements: some courts have limited or excluded expert testimony on specific claims, while others continue to admit it when performed by analysts trained to established protocols. 2
Following Daubert-standard admissibility challenges, courts have divided on whether bloodstain pattern analysis testimony meets reliability requirements: some courts have limited or excluded expert testimony on specific claims, while others continue to admit it when performed by analysts trained to established protocols.
What It ExaminesSourced to the subject's own account
The size, shape, distribution and location of bloodstains, read for the actions and positions that could have produced them. 1
Formalized Year
1971 1
Sourced to the subject's own accountThe year of MacDonell's Flight Characteristics and Stain Patterns of Human Blood.
Known Limitation
The 2009 National Academy of Sciences report concluded that the uncertainties associated with bloodstain pattern analysis are enormous and that expert opinions in the field were generally more subjective than scientific. 2
Cross-Tradition Connections

Associated With

Bloodstain pattern analysis is one of the physical evidence disciplines crime scene reconstruction draws on directly.

Sources
1. Wikipedia: Bloodstain Pattern Analysis
2. Strengthening Forensic Science in the United States: A Path Forward
Quote
The uncertainties associated with bloodstain pattern analysis are enormous.
View the Source
Wikipedia: Crime Reconstruction
Associated With: Crime Scene Reconstruction, IntroductionView the Source
Dissenting Readings (1 dissenting reading)
Known Limitation

Bloodstain pattern analysis practitioners and certifying bodies maintain that the discipline rests on established physics of fluid dynamics and that analysts trained and tested to IABPA and SWGSTAIN protocols produce reliable, court-admissible conclusions; they argue the 2009 NAS critique targeted a lack of published statistical validation studies rather than the method's underlying physical principles, and point to post-Daubert rulings that have continued to admit qualified BPA testimony.

A dissenting reading, from International Association of Bloodstain Pattern AnalystsStrengthening Forensic Science in the United States: A Path Forward

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