Validation of Toolmark Comparisons Made at Different Vertical and Horizontal Angles.

• NCJ Number: 252318
• Author(s): Chad Macziewski; Ryan Spotts; Scott Chumbley
• Date Published: December 2016
• Length: 8 pages
• Grant Number(s): 2011-DNR-0230
• Agencies: NIJ-Sponsored
• Publication Type: Research (Applied/Empirical); Report (Study/Research); Report (Grant Sponsored); Program/Project Description

Annotation

This study involved an analysis of striated toolmarks made as a function of varying vertical and horizontal angles of attack.

Abstract

Numerous studies have focused on determining whether objective statistical methods can be used to discriminate between known matches and nonmatches when comparing laboratory prepared toolmarks. In the current study, comparisons based on experimental data show that replicate toolmarks from the same tool produce high correlation values at identical vertical and horizontal angles, with the correlation decreasing as the angular difference increases, especially for horizontal angular changes. Comparisons between nonmatching samples produce low correlation values that remain unchanged as horizontal angular differences increase. Although complete statistical separation was not achieved between matching and nonmatching samples, there was evidence that demonstrates toolmarks can be identified if the variation in horizontal angle is within 10 degrees. The experiment shows that computer‐aided comparison techniques could be viable for identification with the proper statistical algorithm. (Publisher abstract modified)