Physical and Chemical Trace Evidence from 3D-Printed Firearms

Rapid advances in 3D-printing technology have created an emerging class of firearms that we know almost nothing about, forensically speaking. As the movement to self-manufacture firearms with 3D-printing technology grows, it is reasonable to assume that they will be used in more crimes. Printed plastic guns are also of concern to public safety because they can potentially go undetected by metal detectors into high security areas, and to criminal justice because they do not bear traceable serial numbers. The purpose of this research project to provide criminal justice practitioners the tools they need to investigate, solve, and prosecute 3D-printed gun crimes as well as they do crimes committed with traditional guns. To that end, we will systematically analyze physical and chemical trace evidence from 3D-printed firearms. The use of Direct Analysis in Real Time Mass Spectrometry (DART-MS) for polymer analysis will form the basis of the research, leading to the establishment of a spectral library of 3D-printed polymers for use by forensic practitioners.
*To facilitate DART-MS analysis and physical evidence, we will collaborate with JEOL USA, Inc., the Alabama Department of Forensic Science, and the Mississippi Crime Laboratory.
*The research is divided into three major tasks: (1) printing, test-firing, and collecting physical and chemical trace evidence from 3D-printed guns; (2) analyzing tool mark and impression features evidence using standard forensic techniques, and (3) developing and validating a new method to rapidly detect and identify polymers in the evidence using DART-MS. Analysis of physical evidence will address the use of comparison microscopy to establish toolmark and impression evidence on cartridge cases and bullets from 3D-printed firearms. Analysis of chemical trace evidence will address the analysis of polymers left behind on cartridge cases and bullets by DART-MS for spectral characterization, comparison, and sourcing. We hypothesized that impressions and toolmarks left behind on ammunition components by 3D-printed firearms will be insufficient for individualization back to a specific firearm. Thus, the role of chemical trace analysis by DART-MS aims to (1) compensate for the current void in forensic procedures relating to 3D-printed firearms and to (2) greatly enhance forensic practitioners’ ability to differentiate evidence from crimes involving 3D-printed firearms.
*For DART-MS data analysis, Mass Mountaineer software will provide chemometric analyses including PCA and LDA.
*This research will produce multiple fundamental scientific papers in peer-reviewed journals and a reference library of DART mass spectra of commercially available 3D-printer polymers.
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