The effect of weathering on bullet and cartridge case analysis and identification

Abstract

Currently, there is a void in the literature concerning the natural weathering of bullets exposed to different types of soils with varying acidity levels, mineral compositions, microorganisms, and oxygen saturation levels. The effect of weathering on bullet and cartridge case surfaces needs to be assessed. This may prove important in case work where ammunition components have been recovered from outdoor crime scenes, particularly after a length of time. This study examined the deterioration of bullets and cartridge cases exposed to soil near the water of Lake Arcadia in Oklahoma. 230 grain, copper-alloy, full metal jacket bullets fired from a Ruger P90, .45 caliber Semi-automatic were used and cartridge cases from a Hi-Point JCP, .40 caliber semi-automatic pistol were utilized. Microscopic examination of the projectiles was conducted every two weeks for six months to determine if and when the ability to observe individual characteristics was compromised. Examination indicated that prolonged exposure to soil near lake water in Oklahoma caused discoloration, oxidation, and obscured individual characteristics of the bullets resulting in varied conclusions when compared to the control bullet to include identifications and inconclusives. The cartridge cases were not as impacted by prolonged exposure to this soil. Individual characteristics were observed for all cartridges and identifications made for all comparisons to the control.