100% nitroglycerin appears adequate for many gunshot residues (GSRs). For unburnt powders, 90% nitroglycerin and 10% diphenylamine appear adequate for most powders, and 90% dinitrotoluene and 10% diphenylamine is a possible candidate to increase generalization to powders that contain dinitrotoluene instead of nitroglycerin. Analyses suggest four potential vapor compositions for imprinting. The observed vapor concentration mixing ratios for nitroglycerin and diphenylamine from residues were in the part-per-billion to part-per-trillion range, which would be challenging to detect for many field-deployed explosive vapor detectors and indicate continued importance of canines for forensic investigation and crime prevention. In addition, measurements were taken to track nitroglycerin and diphenylamine vapor concentration changes over time on the spent casings and gun barrels of four types of ammunition. Statistical analysis was conducted on the smokeless powder database maintained by the National Center for Forensic Science, and headspace measurements targeting nitroglycerin and diphenylamine were collected from several powders. In response, this paper reports a set of potential imprinting vapor(s) that may help detection canines generalize across a variety of double-base smokeless powders and gunshot residues. However, there are hundreds of possible smokeless powder formulations across various manufacturers, presenting a challenge for trained canines to generalize across all possible powder compositions. Explosive detection canines can also detect concealed firearms provided that they are imprinted on materials that may be related to firearms such as nitroglycerin in double-base smokeless powders. Non-intrusive means to detect concealed firearms based on magnetometry are widely accepted and employed worldwide.

Pearson .cdf files