NCJ Number
192035
Journal
Journal of Forensic Sciences Volume: 46 Issue: 6 Dated: November 2001 Pages: 1352-1357
Date Published
November 2001
Length
6 pages
Annotation
Firearms incidents in Australia commonly involve 0.22 caliber rimfire ammunition; this paper reports on work that has confirmed the nonhomogeneous nature of gunshot residue (GSR) particles from such ammunition; it has also determined that the lead and barium distribution within particles varies significantly with the particle size and structure.
Abstract
The firearm used for all investigations was a 0.22 LR 4-in. barrel Smith and Wesson Model 18/3 revolver. Winchester Super Speed 0.22 LR (copper-plated projectile) ammunition was used for samples 1 to 4 and Fiocchi 0.22 LR ammunition was used for sample 5. Samples 1 and 2 were collected by tape-lifting both hands of two subjects 20 minutes after each had fired three shots using the same Winchester rimfire ammunition. The samples were analyzed by scanning electron microscopy (SEM), equipped with an energy dispersive X-ray detector for particles that contained lead and barium; they were re-examined for particles that contained lead only. Sample 3 was obtained by tape-lifting the hands of a subject after six rounds of Winchester 0.22 rimfire ammunition had been fired. The sample was examined manually by SEM, and particles located randomly in the size range of less than 3mm and greater than 5 mm were analyzed. In order to determine whether there was a trend between particle morphology and composition and to further assess the trend between particle size and composition, two experiments were performed. The hands of a subject were sampled after multiple rounds of Winchester and Fiocchi brand 0.22 caliber ammunition had been fired from a revolver. The results obtained from these two experiments were compared to GSR particles analyzed in an actual case that involved a suicide. Results from samples 1 and 2 indicate that only a small fraction of the particles produced when 0.22 rimfire ammunition is fired from a revolver can be expected to contain both lead and barium. Further, barium tended to be associated with the larger particles, and the smaller particles tended to be composed of lead with no barium evident. GSR particles obtained from samples 4 (Winchester) and 5 (Fiocchi) showed a clear size-composition and morphology-composition relationship. The observed nonhomogeneous distribution of elements and significant composition variation as a function of particle size apparently contradicts results obtained in a recent study by Lebiedzik and Johnson; however, the ammunition used in their study was not limited to 0.22 caliber ammunition. 7 figures, 1 table, and 13 references