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Significance of Angle in the Statistical Comparison of Forensic Tool Marks

NCJ Number
Technometrics Volume: 55 Issue: 4 Dated: 2013 Pages: 548-561
A. B. Hoeksema; M. D. Morris
Date Published
14 pages

Since the current practice of identifying matching tool marks involves visual inspection of marks by forensic experts, which can be a subjective process that has often been successfully challenged in court, the study reported in this article examined the significance of angle in the statistical comparison of forensic tool marks.


The analysis was based on comparisons of profilometry data, essentially depth contours of a tool mark surface taken along a linear path. Chumbley et al. pointed out that the angle of incidence between the tool and the marked surface can have a substantial impact on the tool mark and on the effectiveness of both manual and algorithmic matching procedures. To better address this problem, this article describes how the analysis can be improved to model the effect of tool angle and allow for angle estimation for a tool mark left at a crime scene. With sufficient development, such methods may lead to more defensible forensic analyses. Data and code are available as supplementary material online. (publisher abstract modified)