A Statistical Validation of the Individuality and Repeatability of Striated Tool Marks: Screwdrivers and Tongue and Groove Pliers

• Published in: Journal of forensic sciences 2010-03, Vol.55 (2), p.348-357
• Main Authors: Bachrach, Benjamin, Jain, Anurag, Jung, Sung, Koons, Robert D.
• Format: Article
• Language: English
• Subjects: 3D imaging; automated comparison of microscopic tool mark evidence; Evidence; forensic science; Forensic sciences; screwdrivers; statistical methodology; striations; Studies; tongue and groove pliers; tool mark identification
• ISSN: 0022-1198; 1556-4029
• DOI: 10.1111/j.1556-4029.2009.01221.x

:  Tool mark identification relies on the premise that microscopic imperfections on a tool’s working surface are sufficiently unique and faithfully transferred to enable a one‐to‐one association between a tool and the tool marks it creates. This paper presents a study undertaken to assess the validity of this premise. As part of this study sets of striated tool marks were created under different conditions and on different media. The topography of these tool marks was acquired and the degree of similarity between them was quantified using well‐defined metrics. An analysis of the resulting matching and nonmatching similarity distributions shows nearly error‐free identification under most conditions. These results provide substantial support for the validity of the premise of tool mark identification. Because the approach taken in this study relies on a quantifiable similarity metric, the results have greater repeatability and objectivity than those obtained using less precise measures of similarity.