Skip to content

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

Journal: Journal of Forensic Sciences
Published: 2019
Primary Author: Ganesh Krishnan
Secondary Authors: Heike Hofmann
Research Area: Firearms and Toolmarks

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.

Related Resources

CSAFE 2020 All Hands Meeting

CSAFE 2020 All Hands Meeting

The 2020 All Hands Meeting was held May 12 and 13, 2020 and served as the closing to the last 5 years of CSAFE research and focused on kicking off…
Comparison of three similarity scores for bullet LEA matching

Comparison of three similarity scores for bullet LEA matching

Recent advances in microscopy have made it possible to collect 3D topographic data, enabling more precise virtual comparisons based on the collected 3D data as a supplement to traditional comparison…
A Robust Approach to Automatically Locating Grooves in 3D Bullet Land Scans

A Robust Approach to Automatically Locating Grooves in 3D Bullet Land Scans

Land engraved areas (LEAs) provide evidence to address the same source–different source problem in forensic firearms examination. Collecting 3D images of bullet LEAs requires capturing portions of the neighboring groove…
Pattern Evidence Research in CSAFE-An Update

Pattern Evidence Research in CSAFE-An Update

CSAFE is a NIST Center of Excellence in Forensic Science. A large portion of CSAFE’s research portfolio is on what is known as pattern evidence, which encompasses any evidence that…
Do you have 44.03 seconds?

44.3 Seconds. That is the average amount of time it takes for a visitor to provide site feedback.
Test it yourself by taking the survey.


A scientist/researcherA member of the forensic science communityA journalist/publicationA studentOther. Please indicate.


Learn more about CSAFE overall.Discover research CSAFE is undertaking.Explore collaboration opportunities.Find tools and education opportunities.Other. Please indicate.


YesNo