NCJ Number
230162
Date Published
August 2009
Length
38 pages
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.