Topic: Noblis/NIST Forensic Bullet Examination Black Box Study Published

[Alan Zheng]

Hicklin RA, Parks CL, Dunagan KM, Emerick BL, Richetelli N, Chapman WJ, Taylor M, Thompson RM. (2024). “Accuracy and Reproducibility of Bullet Comparison Decisions by Forensic Examiners.” Forensic Science International, 365(112287). https://doi.org/10.1016/j.forsciint.2024.112287

This link (https://authors.elsevier.com/a/1k5mM1MCG0dvPk) allows FREE downloading of the paper until 2 January 2025.

Please note that in addition to the main article, extensive information is included in supplemental information, including
Detailed appendices (https://ars.els-cdn.com/content/image/1-s2.0-S0379073824003694-mmc1.pdf),
All response data in data tables (https://ars.els-cdn.com/content/image/1-s2.0-S0379073824003694-mmc2.xlsx),
Images of the comparison sets used in the study (https://doi.org/10.17605/OSF.IO/6XAMU).

The study was conducted by Noblis and NIST under NIST Cooperative Agreement 70NANB18H232.

For all Noblis forensic science publications, please see https://noblis.org/publications/.
 
Abstract
Few previous studies have assessed the accuracy and reproducibility of bullet comparison decisions by firearms examiners, and none have evaluated accuracy of examiners’ decisions when comparing damaged bullets, comparisons of questioned bullets, or the effects on decision rates of using jacketed hollow-point vs. full metal jacket bullets. In this study, 49 practicing forensic firearms examiners conducted 3,156 comparisons of bullets, including bullets ranging in quality, bullets from different types of ammunition, and bullets fired from various makes/models of firearms. The study evaluated two scenarios commonly used in casework: questioned-questioned (QQ) comparisons of two bullets from unknown sources, and known-questioned (KQ) comparisons in which a bullet from an unknown source is compared to three known exemplars from a single firearm. Key findings: after controlling for other factors, QQ vs. KQ comparisons had relatively limited effects on decision rates; rates of inconclusive responses were inversely related to bullet quality; bullets fired from polygonally-rifled pistols resulted in more inconclusive or unsuitable responses than conventional rifling; on nonmated comparison sets, the rate of (true) exclusions was particularly high when comparing different caliber bullets, and was higher on comparisons of different makes/models of firearms vs. the same model of firearm; comparisons in which different types of ammunition were fired from the same firearm had a high rate of erroneous exclusions; decision rates differed notably by firearm model; decision rates varied notably among the participants. Because the measured rates vary dramatically due to these various factors, we recommend against using overall decision rates to summarize the results of this study.

[Robert Thompson]

Alan,
Thanks for posting this!  Saved me some time!