FIREARM CARTRIDGE CASE COMPARISON BY GRAPHITE-FURNACE ATOMIC-ABSORPTION SPECTROCHEMICAL DETERMINATION OF NICKEL, IRON AND LEAD

Graphite furnace atomic absorption spectrometry was used to determine the concentrations of nickel, iron, and lead in 26 different production lots of Winchester-Western cartridge case brass. In most cases, the measured elemental concentrations were found to be normally distributed within a lot, and the variables lacked any strong association. It was found that the concentrations of these three elements could be used as a basis for the comparison of individual cartridge cases to determine their provenance. Using the T-test with a significance level of 0.01, the frequency of obtaining a 'true match' and a 'false match' were found to be 98.1% and 0.43%, respectively. Additionally, a likelihood ratio was used to evaluate the extent to which provenance, or ''common origin'' among brass cartridge cases can be established.