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Evaluation of 3D Virtual Comparison Microscopy for Firearm Forensics within the Crime Lab

NCJ Number
Ryan Lilien
Date Published
December 2020
63 pages

With the goal of advancing the field of 3D scanning and analysis for firearm forensics, this project 1) investigated the effect of scan resolution on an examiner’s ability to reach accurate conclusions and 2) deployed scanning systems to two crime labs and evaluated the use of virtual comparison microscopy (VCM) within the labs.


The completed work includes critical steps in further validating the field of toolmark examination and the use of 3D scanning technology in the forensic lab. The comparison of cartridge cases is based on the observation that microscopic firearm imperfections can be transferred to ammunition during firing. The ability to certify two cartridge cases as similar is a function of both the ability to capture and visualize a high-resolution measurement of each specimen and the ability to identify and match relevant structural features between the two. This 1-year project continued the research and development of the researchers’ novel technology to advance 3D Virtual Comparison Microscopy (VCM). Researchers named the study the Virtual Comparison Microscopy Topography Resolution Study (VCMTRS). Completion of this study required assembly and design of the test datasets, participant recruitment, front-end VCM software development, back-end development of the server architecture to support data distribution and collection, support of participants, assembly of results, and summary of performance. The results obtained in the VCMTR Study provide another pillar of support for the use of the project’s VCM hardware and software within the crime lab. 32 figures, 2 tables, and 21 references