Evaluation of a photoluminescence technique for the detection of gunshot residue.

More than 170 gunshot residue samples were analyzed by the inorganic luminescence technique to assess various factors affecting the utility of this and similar methods of elemental gunshot residue detection. Indoor firings consistently produced more residue in samples than did outdoor firings. Experiments were conducted to determine the effects of activity after firing on the ability to subsequently detect residue in samples. It was shown that residue can be transferred from hand to hand and can be detected in pockets under suitable conditions. Antimony, when present in the ammunition, was found to be the most useful indicator for the presence of residue, in that nearly all firings resulted in more Sb than was found in any of 45 handblank analyses obtained in these studies. Data obtained with a .32 pistol suggest that Sb normally exceeds environmental levels when residue is collected from the hand following delays up to several hours after firing. However, it will rarely exceed the currently used threshold levels of 0.1 to 0.2 microgram. Therefore, elemental analysis is best suited to screening applications for which threshold levels can be greatly reduced.