Objective Evaluation of Subclass Characteristics on Breech Face Marks.

Riva, Fabiano; Hermsen, Rob; Mattijssen, Erwin; Pieper, Pascal; Champod, Christophe (2017). Objective Evaluation of Subclass Characteristics on Breech Face Marks. Journal of forensic sciences, 62(2), pp. 417-422. Wiley 10.1111/1556-4029.13274

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Subclass characteristics can be found on the breech face marks left on spent cartridge cases. Even if they are assumed to be rare and their reported number is small, they can potentially lead to false associations. Subclass characteristics have been studied empirically allowing examiners to recognize them and to understand in which conditions they are produced. Until now, however, their influence on the identification process has not been studied from a probabilistic point of view. In this study, we aim at measuring the effect of these features on the strength of association derived from examinations involving subclass characteristics. The study takes advantage of a 3D automatic comparison system allowing the calculation of likelihood ratios (LRs). The similarities between cartridge case specimens fired by thirteen S&W .40S&W Sigma pistols are quantified, and their respective LRs are computed. The results show that the influence of subclass characteristics on the LRs is limited, even when these features are prevalent among the potential sources considered in a case. We show that the proportion of firearms sharing subclass characteristics should be larger than 40% of the pool of potential firearms for the effect to be significant.

Item Type:

Journal Article (Original Article)

Division/Institute:

04 Faculty of Medicine > Service Sector > Institute of Legal Medicine
04 Faculty of Medicine > Service Sector > Institute of Legal Medicine > Forensic Physics (Ballistics)

UniBE Contributor:

Riva, Fabiano

ISSN:

0022-1198

Publisher:

Wiley

Language:

English

Submitter:

Antoinette Angehrn

Date Deposited:

16 Feb 2017 09:44

Last Modified:

03 Mar 2017 01:31

Publisher DOI:

10.1111/1556-4029.13274

PubMed ID:

27921288

Uncontrolled Keywords:

3D topographies; cartridge cases; evaluation; firearm identification; forensic science; likelihood ratio; subclass characteristics

BORIS DOI:

10.7892/boris.93253

URI:

https://boris.unibe.ch/id/eprint/93253

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