Volume 19, Issue 4 (October 1974)
New Method for the Collection and Analysis of Gunshot Residues as Forensic Evidence
The detection of firearm discharge residues is of great importance in various criminal investigations involving the use of a firearm. One of the procedures introduced in the early 1930s was the “diphenylamine-sulfuric acid dermal nitrate test” on paraffin casts for the presence of nitrites and nitrates from gunpowder discharge residues. However, the limitations of these procedures were pointed out in 1935 and later in 1940 by the Federal Bureau of Investigation [1,2]. In spite of the known limitations of this procedure, the use of diphenylamine tests to detect gunpowder residues continued because of the lack of other suitable test procedures to satisfy this need in criminal investigations. In 1959, Harrison and Gilroy  demonstrated the presence of barium (Ba), antimony (Sb), and lead (Pb) in the firearm discharge residues and devised qualitative chemical tests to identify the presence of these elements, thus offering a unique new method to detect gunshot residues. Because of the limitations in the sensitivity of the colorimetric reactions used to detect Ba, Sb, and Pb, there was no widespread adoption of this method to replace the classical “diphenylamine test.” The continued use of this test to identify gunshot residues is of great concern and this concern was eloquently expressed by practicing forensic chemists Cowan and Purdon . Because of the rapid increase in new products for consumers, numerous materials around a person's environment can develop a positive reaction to the diphenylamine tests. This fact is now generally recognized, although the use of the diphenylamine test has not been altogether abandoned.