The study found that 37 percent of the samples taken from the exteriors of the four tested firearms yielded DNA quantities suitable for further processing, with an average yield of 1.1 ng of DNA per sample. DNA recovery was most successful in samples taken from the grip of all four firearms and the slide serrations of the pistol. A link between the shooter and the DNA profile obtained was established for 30 percent of the samples. In most cases, the shooter could not be excluded as the major contributor to the mixture; however, there were instances in which the shooter could only be attributed to the mixture as a minor contributor of DNA. The remaining 70 percent of samples did not yield sufficient DNA, or the profiles obtained were partial or complex mixtures. Only 2 of the 72 experimental samples of fired cartridge cases, unfired cartridges, and the top and sides of the magazine of a pistol yielded DNA quantities above the 240 pg amplification threshold. Only the magazine sample yielded a full nine STR (short tandem repeat) locus DNA profile that was attributable to the shooter. Samples from the cartridge cases discharged from the firearm and loaded unfired cartridges both showed loss and degradation of DNA. Four firearms were used in the study: a revolver, a pistol, a break-action shotgun, and a pump-action shotgun. A Colt, 1911 Series Combat Elite, Mark IV semiautomatic pistol was used with Winchester .45 ACP cartridges for the portion of the study that examined success rates of DNA recovery from cartridges, cartridge cases, and the magazine of this firearm. 7 figures, 1 table, and 13 references