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Accuracy and Reproducibility of Conclusions by Forensic Bloodstain Pattern Analysts

NCJ Number
Forensic Science International Volume: 325 Dated: August 2021
Date Published
August 2021

This article reports on a study that 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.


This study was conducted because the analysis of bloodstain pattern evidence left at crime scenes relies on the expert opinions of bloodstain pattern analysts; however, the accuracy and reproducibility of these conclusions have never been rigorously evaluated at a large scale. The results of the current study show that conclusions were often erroneous and contradicted other analysts. On samples with known causes, 11.2 percent of responses were erroneous. The results show limited reproducibility of conclusions: 7.8 percent 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. (publisher abstract modified)

Date Published: August 1, 2021