Bloodstain Pattern Analysis Black Box Study

Austin Hicklin, director of the Noblis forensic science group, co-presented findings of a bloodstain pattern analysis black box study as part of a webinar series produced by the Center for Statistics and Applications in Forensic Evidence (CSAFE). The study, entitled “Accuracy and Reproducibility of Conclusions by Forensic Bloodstain Pattern Analysts”1 and published by Forensic Science International, is posted here.

Watch the full webinar:

About the Study

This study was conducted to assess the accuracy and reproducibility of Bloodstain Pattern Analysis (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 regarding 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.

1 Hicklin RA, Winer KR, Kish PE, Parks CL, Chapman W, Dunagan K, Richetelli N, Epstein EG, Ausdemore MA, Busey TA (2021) “Accuracy and Reproducibility of Conclusions by Forensic Bloodstain Pattern Analysts” Forensic Science International 2021, 110856, ISSN 0379-0738, https://doi.org/10.1016/j.forsciint.2021.110856