Identification of polymers and organic gunshot residue in evidence from 3D-printed firearms using DART-mass spectrometry: A feasibility study

Abstract

Rapid advances in 3D-printing technology have created an emerging class of firearms. As the movement to self-manufacture firearms with 3D-printing grows, it is reasonable to assume that they will be increasingly used in crimes. Here, we test-fired gun barrels made with acrylonitrile butadiene styrene (ABS), polylactic acid (PLA), polyethylene terephthalate (PETG), chlorinated polyethylene (CPE), and nylon. The resulting cartridge cases, bullets, and gunshot residue (GSR) were examined by direct analysis in real time – mass spectrometry (DART-MS). High-resolution mass spectra detected polymer from the gun barrel on bullets and cartridge casings for a 0.38 special caliber gun and, to a lesser extent, for a 0.22 caliber 3D-printed gun. Particles of plastic were identified in some GSR samples collected from clothing used as a backstop for test-fires. DART-MS also readily detected signature organic GSR compounds, including methyl centralite, ethyl centralite, diphenylamine, and nitrocellulose, on recovered bullets, cartridge cases, and in extracts of SEM stubs used to collect GSR from the clothing. Overall, this study demonstrates that analysis of firearm trace evidence using DART-MS deserves more attention, and that the technique may be particularly useful for investigating crimes involving 3D-printed guns.