A Study of the Presence of Gunshot Residue in Pittsburgh Police Stations using SEM/EDS and LC-MS/MS

Due to possible secondary transfer of gunshot residue (GSR) onto a suspect in police custody prior to sampling, a baseline must be created for the amount of GSR present. With an increase of "lead free" ammunition, testing for both gunpowder and primer GSR is relevant. Seventy samples were collected using carbon-coated adhesive stubs from four Pittsburgh Police Stations and vehicles to investigate these locations as sources of secondary GSR contamination. These seventy samples were analyzed for primer GSR using scanning electron microscopy-energy-dispersive X-ray spectrometry. One primer GSR particle was detected; no sample was classified as positive for primer GSR. These same samples were then analyzed for gunpowder GSR using liquid chromatography coupled to tandem mass spectrometry to test for akardite II, ethylcentralite, diphenylamine, N-nitrosodiphenylamine, 2-nitrodiphenylamine, and 4-nitrodiphenylamine. Ethylcentralite was quantifiable in two test samples. These results suggest there is a negligible potential for secondary transfer of primer and gunpowder GSR.