NCJ Number
186434
Journal
Journal of Forensic Sciences Volume: 45 Issue: 6 Dated: November 2000 Pages: 1316-1319
Date Published
November 2000
Length
4 pages
Annotation
A cleaning procedure for seriously weathered or corroded bullets and cartridge casings was developed and implemented for evidence specimens from a multiple homicide.
Abstract
The restoration protocol entailed successive treatments with increasingly aggressive chemical solvents and cleaning solutions while monitoring the progress of the method by optical microscopy. The treatment of worst-case Cu-alloy jacketed bullets and casings resulted in reconditioned specimens that subsequently underwent successful firearms examinations. The appropriate exposure time of a specimen in each cleaning solution was optimally determined on an individual basis for a given application. For this questioned evidence, minimal times and ultrasonic agitation were important. Of particular consequence was the careful control of the length of time the specimens were exposed to acidic thiourea, which should not be beyond that required to remove surface contamination. The complete protocol was effective in loosening miscellaneous debris and dissolving the corrosion to expose the underlying Cu-Zn jacket; however, optical microscopy showed that any fine striae or other characteristic markings had been obliterated by the years of organometallic reactions within the interior of the tree in which the bullets had been embedded. Casings (9 mm) found on the grounds of the crime-scene residence were cartridge brass. The qualitative improvement in the external appearance of these casings as the result of the cleaning treatments was extremely good, and forensic comparisons of firing-pin, breach-face, ejector, and extractor striae with those of the crime-scene 9-mm casings became possible. The result was positive matches of four residence casings with the crime-scene specimens. 5 figures and 4 references