This CSAFE webinar was held on October 14, 2021.
Noblis Forensic Science Group, Director
Forensic Consultant, Paul Erwin Kish Forensic Consultant and Associates
Director, Kansas City Police Crime Laboratory
This study was conducted to assess the accuracy and reproducibility of BPA conclusions. Although the analysis of bloodstain pattern evidence left at crime scenes relies on the expert opinions of bloodstain pattern analysts, the accuracy and reproducibility of these conclusions have never been rigorously evaluated at a large scale. We investigated conclusions made by 75 practicing bloodstain pattern analysts on 192 bloodstain patterns selected to be broadly representative of operational casework, resulting in 33,005 responses to prompts and 1,760 short text responses. Our results show that conclusions were often erroneous and often contradicted other analysts. On samples with known causes, 11.2% of responses were erroneous. The results show limited reproducibility of conclusions: 7.8% of responses contradicted other analysts. The disagreements with respect to the meaning and usage of BPA terminology and classifications suggest a need for improved standards. Both semantic differences and contradictory interpretations contributed to errors and disagreements, which could have serious implications if they occurred in casework. Paul Kish, Kevin Winer, and Noblis conducted the study under a grant from the U.S. National Institute of Justice (NIJ).
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