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Despite the importance of tool mark analysis in the forensic sciences, the imaging and comparison of tool marks remains a difficult and time-consuming endeavor. Cartridge case comparison is based on the observation that microscopic firearm imperfections can be transferred to a fired cartridge case. Therefore, two cases with highly similar breech-face impressions are likely to have been fired through the same firearm.

The ability to certify two cases as highly similar is therefore a function of both the ability to capture a high-resolution measurement of each case and the ability to identify and match relevant structural features.

The next generation of methods for the forensic analysis of tool marks should improve accuracy, reduce acquisition and operational costs, and shorten analysis time. The author’s platform utilized the recently developed GelSight surface topography imaging system and a custom feature-based image comparison software.

The TopMatch-GS 3D was able to accurately capture and compare high-resolution, three-dimensional surfaces. The authors achieved excellent performance on good marking casings and surprisingly good performance on extremely challenging casings — casings that a firearms expert claims would be difficult and time consuming to match. Most importantly, there were no false-positives across approximately 200,000 comparisons.

Read the report, "Applied Research and Development of a Three-Dimensional Topography System for Firearm Identification Using GelSight."

Source: NIJ

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