Adapting the Chumbley Score to Match Striae on Land Engraved Areas (LEAs) of Bullets

Thumbnail Image
Date
2019-05-01
Authors
Krishnan, Ganesh
Hofmann, Heike
Major Professor
Advisor
Committee Member
Journal Title
Journal ISSN
Volume Title
Publisher
Authors
Research Projects
Organizational Units
Organizational Unit
Center for Statistics and Applications in Forensic Evidence
The Center for Statistics and Applications in Forensic Evidence (CSAFE) carries out research on the scientific foundations of forensic methods, develops novel statistical methods and transfers knowledge and technological innovations to the forensic science community. We collaborate with more than 80 researchers and across six universities to drive solutions to support our forensic community partners with accessible tools, open-source databases and educational opportunities.
Journal Issue
Is Version Of
Versions
Series
Department
Center for Statistics and Applications in Forensic Evidence
Abstract

The same‐source problem remains a major challenge in forensic toolmark and firearm examination. Here, we investigate the applicability of the Chumbley method (J Forensic Sci, 2018, 63, 849; J Forensic Sci, 2010, 55, 953) (10,12), developed for screwdriver markings, for same‐source identification of striations on bullet LEAs. The Hamby datasets 44 and 252 measured by NIST and CSAFE (high‐resolution scans) are used here. We provide methods to identify parameters that minimize error rates for matching of LEAs, and a remedial algorithm to alleviate the problem of failed tests, while increasing the power of the test and reducing error rates. For 85,491 land‐to‐land comparisons (84,235 known nonmatches and 1256 known matches), the adapted test does not provide a result in 176 situations (originally more than 500). The Type I and Type II error rates are 7.2% (6105 out of 84,235) and 21.4% (271 out of 1256), respectively. This puts the proposed method on similar footing as other single‐feature matching approaches in the literature.

Comments

This is a manuscript of an article published as Krishnan, Ganesh, and Heike Hofmann. "Adapting the Chumbley Score to Match Striae on Land Engraved Areas (LEA s) of Bullets." Journal of forensic sciences 64, no. 3 (2019): 728-740. Posted with permission of CSAFE.

Description
Keywords
Citation
DOI
Copyright
Mon Jan 01 00:00:00 UTC 2018
Collections