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NCJRS Abstract

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NCJ Number: 230162 Find in a Library
Title: Quantification of Toolmarks, Final Technical Report
Author(s): L. S. Chumbley
Date Published: August 2009
Page Count: 38
Sponsoring Agency: National Institute of Justice (NIJ)
Washington, DC 20531
National Institute of Justice/NCJRS
Rockville, MD 20849
NCJRS Photocopy Services
Rockville, MD 20849-6000
Grant Number: 2004-R-IJ-088
Sale Source: National Institute of Justice/NCJRS
Box 6000
Rockville, MD 20849
United States of America

NCJRS Photocopy Services
Box 6000
Rockville, MD 20849-6000
United States of America
Document: PDF
Type: Report (Study/Research)
Format: Document
Language: English
Country: United States of America
Annotation: The goal of this research was to develop a methodology to characterize toolmarks using quantitative measures of the three-dimensional nature of the mark, rather than a two-dimensional image of the mark.
Abstract: Results from this research suggest that it can be concluded that an objective method of toolmark comparison is feasible as a screening process, and that related contextual information should be included in this process in order to enhance findings. However, an experienced examiner is still essential in verifying the actual results of any computer-based algorithm. Once such a methodology was developed in which objective comparisons between two toolmarks could be made to determine whether marks made from similar tools could be distinguished quantitatively from marks made using other tools. The toolmarks studied were produced using 50 sequentially manufactured screwdriver tips that had not seen service. The algorithm developed to allow comparison of two scans in an objective, quantitative manner mimics the procedure used by forensic. Initial results showed that known matches, or marks made by the same screwdriver, could be identified on average 95 percent of the. In an effort to improve the result, a study involving actual examiners was conducted. In this study the examiners yielded a higher degree of success than the algorithm, however examiners are trained to only make a positive ID when absolutely certain whereas the algorithm is not as selective. Overall, this comparison revealed that contextual information plays a large role in the examiner’s decision-making process while such information was purposefully omitted from the initial trials of the algorithm in order to make its operation as general as possible. A final study including contextual information was conducted, and the results were vastly superior to those obtained when this information was omitted.
Main Term(s): Police policies and procedures
Index Term(s): Evidence identification; Forensic sciences; Investigative techniques; Toolmark identification
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