Department of Chemistry, SUNY College of Environmental Science and Forestry, Syracuse, NY
Advanced Research Instruments Corp., Boulder, CO
(Received 15 January 1999; accepted 10 May 1999)
Automated scanning electron microscopy coupled with image analysis and X-ray micro analysis was used to characterize a variety of gunshot residue (GSR) samples. More than 500 rounds of commercially available ammunition and six different types of hand guns were used in the study of 17 GSR and 19 reference specimens. The individual particle X-ray composition was determined for 12 different elements. Elemental composition of GSR particles was highly variable but consistent with compounds mixed into or associated with a barium oxide matrix. When present in a specimen, GSR could be adequately characterized with automated procedures in less than an hour by restricting analyses to features larger than 2 µm. In “clean” samples, a higher resolution particle search was required to avoid reporting false negatives. Careful control of the back scattered electron signal strength threshold, by reference to a standard, was needed to ensure both time-efficient and accurate analyses. Samples collected from non-shooting subjects, active in a physical environment which contained firearms discharge residue were seen to be easily contaminated by sub-micron GSR particles.
Paper ID: JFS14644J