Firearms and Toolmarks

When bullet marks, bullets or cartridge cases are present at a crime scene, firearm examiners are limited by visual inspections to determine which particular gun was used. Human error and bias can diminish the confidence in the evidence when used in a courtroom testimony.


Pattern Evidence


Statistics, Criminal Justice, Anthropology


  • Collaborated with the National Institute of Standards and Technology (NIST) to develop an algorithm that objectively identifies signature features or a combination of features on each bullet. The algorithm numerically computes the differences and provides examiners a score of the match.
  • Creating an open-source method for computing numerical signatures from cartridge breechface images, developing statistical methods for comparing signatures and addressing statistical modeling not addressed by NIST’s research on identifying characteristics.

Benefits of Research

Examiners can give more-objective testimony of bullet comparison and are able to express an accurate degree of uncertainty in their conclusions; testimony will no longer use definitive language such as “it is a match” or “it is not a match”; experts from both sides of the trial can access and use this technology; suspects can access the technology and review the results.

Select Publications, Conference Papers, Presentations and/or Tools

Bulletr Software

Cartridges Software

Xiao Hui Tai and William F. Eddy. A Fully Automatic Method for Comparing Cartridge Case Images. Journal of Forensic Sciences. Forthcoming 2018.

Presentation, Forensics@NIST, Gaithersburg, MD, November 2016

Presentation, Association of Firearm and Tool Mark Examiners Annual Training Seminar, March 16, 2017.

Hare E., Hofmann H., Carriquiry A. (accepted). Automated Matching of Bullet Lands, Annals of Applied Statistics, acknowledgment of federal support: yes.

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