AFTE Store - An Empirical Study to Improve the Scientific Foundation of Forensic Firearm and Tool Mark Identification Utilizing 10 Consecutively Manufactured Slides

The Miami-Dade Police Department Crime Laboratory conducted a research study on The Repeatability and Uniqueness of Striations/Impressions on Fired Cartridge Casings Fired in 10 Consecutively Manufactured 9mm Ruger Slides to improve understanding of the accuracy, reliability, and measurement validity in the firearm and tool mark discipline of forensic science. The foundation of firearm and tool mark identification is that each firearm/tool produces a signature of identification (striation/impression) that is unique to that firearm/tool, and through the examination of the individual striations/impressions, the signature can be positively identified to the firearm/tool that produced it. The National Academy of Sciences (NAS) Report questioned the repeatability and uniqueness of striations/impressions left on fired evidence as well as the validity and error rate in firearms identification. This study analyzed the repeatability and uniqueness of striations/impressions on fired cartridge cases fired in 10 consecutively manufactured Ruger slides by analyzing breech face striations/impressions through an evaluation of the participants’ accuracy in making correct identifications. One semi-automatic pistol and nine additional consecutively manufactured slides were utilized. Consecutively manufactured slides are significant to this study because they were manufactured with the same equipment/tools. Even though these slides were consecutively made, their signatures should be different. Test sets assembled included test fired casings from each slide, as well as unknowns. Participants were firearm & tool mark examiners throughout the United States. One hundred and fifty-eight test sets were distributed to laboratories in forty-six states and the District of Columbia. The test sets were designed to determine an examiner’s ability to correctly identify cartridge casings fired from 10 consecutively manufactured Ruger Slides to test fired cartridge casings fired from the same slides. This empirical study established an error rate of less than 0.1 percent. Durability testing established that the Ruger Slides maintained their individual signature after multiple firings. This project was supported by Award No. 2009-DN-BX-K230 awarded by the National Institute of Justice, Office of Justice Programs, U. S. Department of Justice. The opinions, findings, and conclusions or recommendations expressed in this publication/program/exhibition are those of the authors and do not necessarily reflect those of the Department of Justice.

Full Journal: AFTE Journal Vol 45 No 4 (2013)