Objective evaluation of subclass characteristics on breech face marks

Details

Serval ID
serval:BIB_3CA1E9AB1191
Type
Article: article from journal or magazin.
Collection
Publications
Institution
Title
Objective evaluation of subclass characteristics on breech face marks
Journal
Journal of forensic sciences
Author(s)
Riva F., Hermsen R., Mattijssen E., Pieper P., Champod C.
ISSN
0022-1198
Publication state
Published
Issued date
2017
Peer-reviewed
Oui
Volume
62
Number
2
Pages
417-422
Language
english
Abstract
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.
Keywords
forensic science, firearm identification, subclass characteristics, likelihood ratio, cartridge cases, 3D topographies, evaluation
Create date
09/03/2017 9:45
Last modification date
03/07/2020 6:21
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