Population Statistics for Firearm Toolmark Analysis

This document contains slides of a presentation given by Xiaoyu Alan Zheng at the 2022 Association of Firearms and Tool Mark Examiners (AFTE) Annual Training Seminar in Atlanta, GA. Preliminary results are presented of a project in which the similarities of 3D images of known matching and known non-matching fired cartridge cases are compared across a range of firearm models and ammunition types. The variation of the resulting Score-based Likelihood Ratio is demonstrated, showing the importance of large reference populations for building appropriately relevant sub-populations.