Volume 21, Issue 1 (January 1976)
Time of Firing of Shot Shells
Estimation of the time lapse since a cartridge or a firearm was fired is an important aspect of forensic ballistics. In the past efforts have been made to correlate the time lapse with the chemical changes of the firearm discharge residues. Both qualitative and quantitative variation of the combustion products with the passage of time have been studied by examining barrel washings and dry swabs pushed through the barrel [1,2]. Such examinations, however, did not yield satisfactory results, because, besides the time factor, chemical changes of the discharge residues were found to be significantly influenced by the atmospheric conditions. It was also difficult to extract the total quantity of combustion products by dry or wet methods for correct quantitative estimation. Various other phenomena, such as presence of carbon monoxide, mercury vapour, and pollen grains, have also been utilized by various workers to ascertain the time of firing [2,3]. Their limitations in correlating the time lapse are well known.