SignificanceComprehensive evaluation of a forensic technique's validity should entail consideration of not only error rates, but accuracy and inconclusive rates, as well. The fact that a technique excels at avoiding errors does not ensure that it is equally successful at reaching correct decisions. This research, which focused on cartridge-case comparison, showed that error rates were uniformly low, but other performance measures varied by the firearm model and the treatment of inconclusive decisions. Importantly, inconclusive decisions occurred frequently and predicted different-source status, the ground-truth state supportive of factual innocence. Mindful of the probative and exculpatory value of inconclusive decisions, prosecutors should disclose inconclusive results to the defense, and defense attorneys should consider inconclusive results as a possible basis for post-conviction actions.