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Publication Citation: 2D and 3D Topography Comparisons of Toolmarks Produced from Consecutively Manufactured Chisels and Punches.

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Author(s): Xiaoyu A. Zheng; Johannes A. Soons; Robert M. Thompson; John Villanova; Taher Kakal;
Title: 2D and 3D Topography Comparisons of Toolmarks Produced from Consecutively Manufactured Chisels and Punches.
Published: May 20, 2014
Abstract: A 2009 report by the National Academies [1] recommended strengthening the scientific basis of procedures and criteria employed by the forensic science specialty of toolmark identification. The current method of comparison and determination of identity is conducted by a trained examiner using a comparison microscope. However, the ultimate conclusion of the comparison is subjective in nature and is affected by the examiner‰s skill and experience. This study seeks to evaluate whether a mathematically objective metric, the maximum value of the Cross Correlation Function (CCF_MAX), can be employed to identify the tool that generated a striated or impressed toolmark from a pool of consecutively manufactured tools. The metric will be applied to the measured surface topography of toolmarks generated under laboratory conditions on a near pristine surface. A device was designed for the controlled generation of toolmarks. Two types of representative tools were selected: chisels for making striated toolmarks and drift punches for making impressed toolmarks. For striated tool marks, a 2D stylus instrument was used to capture the toolmark topography. Impressed toolmark topographies were captured using a 3D disc scanning confocal microscope. The comparisons were blind, with fully automated data analysis and identification. Based on the CCF_MAX metric and a statistical analysis of the known match and known non-match scores, all the unknown toolmarks were correctly identified to the tool that created them. This study provides additional objective scientific support for the validity of toolmark identifications.
Citation: Journal of the Association of Firearms and Toolmarks Examiners
Volume: 46
Pages: pp. 143 - 147
Keywords: toolmark identification; chisel; punch; consecutively manufactured; cross correlation function; impressed tool marks; striated tool marks.
Research Areas: Law Enforcement, Public Safety/Security, Forensics
PDF version: PDF Document Click here to retrieve PDF version of paper (963KB)