FLN-TWG: 3D Imaging for Firearms and Toolmarks

FLN-TWG: 3D Imaging for Firearms and Toolmarks

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Forensic Laboratory Needs Technology Working Group (FLN-TWG)

The National Institute of Justice (NIJ), in partnership with the Forensic Technology Center of Excellence (FTCOE) at RTI International, formed the Forensic Laboratory Needs Technology Working Group (FLN-TWG). The FLN-TWG supports NIJ’s mission to improve knowledge and understanding of the forensic technology needs of federal, state, local, and tribal forensic practitioners and crime laboratories. flntwg

Implementation Strategies: 3D Imaging for Firearms and Toolmarks


October 2021


Forensic laboratories have relied on light microscopy for a multitude of disciplines since the inception of forensic science, including questioned documents, trace evidence, and firearm and toolmark examination. Within the discipline of firearm and toolmark examination, light microscopy has been the traditional means for conducting physical comparisons of microscopic marks on ammunition components and toolmarked surfaces. In the past decade, the application of three-dimensional (3D) imaging methods capable of measuring the x, y, and z coordinates of microscopic features within a toolmark has allowed the development of high-resolution digital images and measurement of the surface topographies of those microscopic features. The advancement in instrumentation used for virtual comparison microscopy allows examiners to view accurate representations of toolmarked surfaces and to collect and measure topographic data from the evidence, facilitating comparisons that are more objective compared with conventional light microscopy comparison methods. This technology enables virtual technical reviews without the physical transfer of evidence. These tools show promise to revolutionize the field of forensic firearms examination and to address the need for more automated, quantitative methods for pattern evidence comparison, as expressed by the National Academies of Science (NAS) and President's Council of Advisors on Science Technology (PCAST) reports. This paper summarizes the current state of 3D imaging technology used in firearm and toolmark forensic analysis and offers guidance to laboratory managers considering adopting this technology. The appendix includes a vendor table listing available instrumentation at the time this document was published.

Funding for this Forensic Technology Center of Excellence report was provided by the National Institute of Justice, Office of Justice Programs, U.S. Department of Justice.

The opinions, findings, and conclusions or recommendations expressed in this report are those of the author(s) and do not necessarily reflect those of the U.S. Department of Justice.

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