Gunshot Residue Analysis and Comparison

Brian Murphy

Bullet casings and gunshot residue (GSR) from five competing manufacturers were analyzed and compared utilizing polarized light microscopy and atomic absorption spectroscopy. GSR was obtained by swabbing the inside of the bullet casings. The bullet casings were prepared by dissolving them in concentrated nitric acid solution. Microcrystalline tests produced crystalline precipitates that were observed microscopically. Reagents were used that selectively reacted with the metal being tested. All samples tested positive for the presence of both lead and iron. Graphite furnace atomic absorption was then utilized to determine the concentrations of several metals (iron, lead, antimony, cadmium, and manganese) and compared among the different manufacturers.

• Brian Murphy is from Bluffton, SC. He is a senior chemistry major with an emphasis in forensic science. He is a cadet in ROTC, and the vice president of the Lander University Microscopy Association (LUMA).