Determining the number of test fires needed to represent the variability present within firearms of various calibers

Forensic Science International : Synergy
Eric F LawCasey M Jelsema

Abstract

The Association of Firearm and Toolmark Examiners recommends a minimum of two test fires be performed when an unknown firearm is submitted to a laboratory prior to doing a comparison with a cartridge case collected from a crime scene. Limited research has been performed to determine how many test fires are necessary to be representative of the match distribution of a firearm. Various makes and models of firearms comprising five calibers were tested using a hybrid equivalence test to determine how many cartridge cases were required to represent the match distribution of an unknown firearm based on both breech face and firing pin correlation scores from an IBIS® HeritageTM System. The same general trend was observed for each caliber of firearm where the equivalence percentage increased from 10 to 30 cartridge cases. Overall, 15 cartridge cases are sufficient for above an 80% probability of representing the full match distribution for an unknown firearm. To approach full equivalence, 25 cartridge cases are enough because 30 cartridge cases were not found to be significantly higher in equivalence percentage for any caliber of firearm tested.

References

Mar 24, 2004·Forensic Science International : Synergy·Jan De KinderHugues Thiebaut
Sep 22, 2010·Journal of General Internal Medicine·Esteban Walker, Amy S Nowacki
Feb 8, 2014·Journal of Forensic Sciences·Fabiano Riva, Christophe Champod
May 22, 2017·Forensic Science International : Synergy·Eric F LawCasey M Jelsema
Dec 27, 2017·Forensic Science International : Synergy·Kaifeng Zhang, Yaping Luo
Jan 1, 2016·Journal of Statistical Software·Casey M Jelsema, Shyamal D Peddada

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Citations

Jan 2, 2021·Forensic Science International : Synergy·Erwin J A T Mattijssen
Jan 2, 2021·Forensic Science International : Synergy·Martin Baiker-SørensenRichard Visser
Jul 27, 2021·Forensic Science International : Synergy·K AlsopM A Williams

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