Accuracy of comparison decisions by forensic firearms examiners |
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Authors: | Keith L Monson PhD Erich D Smith MSFS Eugene M Peters PhD |
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Institution: | Federal Bureau of Investigation Laboratory, Quantico, Virginia, USA |
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Abstract: | This black box study assessed the performance of forensic firearms examiners in the United States. It involved three different types of firearms and 173 volunteers who performed a total of 8640 comparisons of both bullets and cartridge cases. The overall false-positive error rate was estimated as 0.656% and 0.933% for bullets and cartridge cases, respectively, while the rate of false negatives was estimated as 2.87% and 1.87% for bullets and cartridge cases, respectively. The majority of errors were made by a limited number of examiners. Because chi-square tests of independence strongly suggest that error probabilities are not the same for each examiner, these are maximum-likelihood estimates based on the beta-binomial probability model and do not depend on an assumption of equal examiner-specific error rates. Corresponding 95% confidence intervals are (0.305%, 1.42%) and (0.548%, 1.57%) for false positives for bullets and cartridge cases, respectively, and (1.89%, 4.26%) and (1.16%, 2.99%) for false negatives for bullets and cartridge cases, respectively. The results of this study are consistent with prior studies, despite its comprehensive design and challenging specimens. |
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Keywords: | accuracy black box consecutive manufacture decision analysis error rate firearms and toolmark identification foundational validity open set design reliability subclass |
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