A Worldwide Study of Bullets Fired From 10 Consecutively Rifled 9MM RUGER Pistol Barrels—Analysis of Examiner Error Rate

This technical note is an update on a continuing study, first designed and initiated by Brundage et al. over twenty years ago , which seeks to test the community of forensic firearms examiners’ ability to associate fired bullets with the barrels through which they passed. To date, 697 participants have utilized over 240 test sets consisting of bullets fired through 10 consecutively rifled RUGER P‐85 pistol barrels. Here, we report on the results of the ongoing “10‐barrel test” up until the point in time of writing this manuscript. To analyze the totality of data thus far collected, a Bayesian approach was selected. Posterior average examiner error rates are assigned assuming only vague prior information. Given the data found over the course of this diverse decades‐long study, our most conservative value for average examiner error rate has a posterior mean of 0.053% with a 95% probability interval of [1.1 × 10−5%, 0.16%].