by Kenneth Ujevich
The purpose of this experiment was to determine the likelihood of encountering characteristic gunshot residue (GSR) particles in an open environment. This likelihood could affect the results of GSR testing if encountering these characteristic particles turned out to be a relatively common event. “Characteristic” GSR particles are defined as those that contain the elements lead, antimony, and barium, and are spheroidal in shape ranging in size from 0.5 micrometers to 5.0 micrometers in diameter. Other particles that could be considered consistent with GSR were particles that had some combination of two of the three previously listed elements. To test for these particles, 100 upper outer garments were collected in connection to non-firearm related offenses and submitted to a forensic laboratory for examination. 98 of the 100 garments did not contain any of the characteristic 3-component particles. Of the two that did, one contained only 1 characteristic particle while the other contained only 2 particles. When testing for the other particles, 97 garments had 6 or fewer particles present, while the remaining three individual garments had 7, 8, and 22 particles present, respectively. Given the data, the probability of finding one or two 3-component particles on clothing is of the order of 0.02, with the probability of finding more being significantly less than this. The fabric of clothing trapping GSR particles make it more likely that they would be present on clothing than on hands, but the data still shows that this would be a relatively uncommon event.
Thomas J. Hannigan, Sean D. McDermott, Claire M. Greaney, John O’Shaughnessy, Cliona M. O’Brien. “Evaluation of gunshot residue (GSR) evidence: Surveys of prevalence of GSR on clothing and frequency of residue types.” Forensic Science International, Volume 257, December 2015, Pages 177-181, ISSN 0379-0738, http://dx.doi.org/10.1016/j.forsciint.2015.08.003.