The problem with eliminations: Why forensic comparisons need false negative rates

Abstract

This article examines the overlooked risk of false negative errors arising from eliminations in forensic firearm comparisons. While recent reforms in forensic science have focused on reducing false positives, eliminations — often based on class characteristics or intuitive judgments — receive little empirical scrutiny despite their potential to exclude true sources. In cases involving a closed pool of suspects, eliminations can function as de facto identifications, introducing serious risk of error. A review of existing validity studies reveals that many report only false positive rates, failing to provide a complete assessment of method accuracy. This asymmetry is reinforced by professional guidelines, such as those from AFTE, and echoed in major government reports, including those from NAS and PCAST. The article argues that eliminations, like identifications, must be validated through rigorous testing and reported with transparent error rates. It further cautions against the use of “common sense” eliminations in the absence of empirical support and highlights the dangers of contextual bias when examiners are aware of investigative constraints. Five policy recommendations are proposed to improve the scientific treatment and legal interpretation of eliminations, including balanced reporting of false positive and false negative rates, validation of intuitive judgments, and clear warnings against using eliminations to infer guilt in closed-pool scenarios. Without reform, eliminations will continue to escape scrutiny, perpetuating unmeasured error and undermining the integrity of forensic conclusions.