U.S. flag

An official website of the United States government, Department of Justice.

Identifying the Factors Necessary for Successful DNA Profiling From Spent Cartridge Casings

NCJ Number
Date Published
July 2017
334 pages
This report presents the findings and methodology of a research project that tested and optimized methods for obtaining DNA from spent cartridge casings, and it also tested various DNA analysis methods.

Overall, a significantly superior method for isolating and purifying DNA from spent cartridge casings was identified, as were a large number of variables that did or did not affect DNA yields from casings found at crime scenes. The research methodology involved volunteers loading live cartridges into the magazines of firearms, which were fired and casings collected. These collections were used to test several variables that might influence successful DNA analysis from spent cartridges. The first experiments involved swabbing or soaking casings. The optimized protocol consisted of soaking casings in the bulb of a plastic transfer pipette for 30 minutes, removing the liquid, and swabbing the casing and bulb, followed by incubating the swab and solution at 85 degrees C for 10 minutes. The swabbing protocol was a standard double swab strategy in which the first swab is wetted and used to swab the object, followed by a dry swab that collects residual liquid. Finally, a kit specifically designed for DNA isolation from fingerprints (Fingerprint DNA Finder or FDF) was tested, following the manufacturer's instructions. Swabbing resulted in significantly higher DNA yields than did soaking, followed by FDF. Organic extraction resulted in significantly higher DNA yields than QIAamp and FDF. Loading/firing order, which could influence DNA yields in a variety of ways, did not have a discernible impact on DNA yields or typing results. On the other hand, the cartridge's caliber did affect DNA results, with 0.45 caliber casings resulting in greater DNA yields than 0.22 caliber casings. Appended extensive tables

Date Published: July 1, 2017