The uncertain probative value of forensic pattern matching evidence: Implications for reporting and testimony

This article reviews the scientific literature on the probative value of forensic pattern-matching evidence and offers a novel reanalysis of black-box study data on fingerprint and firearm identification accuracy, calculating aggregate likelihood ratios and comparing them systematically to ENFSI verbal labels and DOJ reporting guidelines-an analysis not previously undertaken in the literature. The analysis shows that the probative value is highly uncertain, forensic examiners often overstate the value of such evidence, and lay people tend to believe it is more probative than it actually is. The implications of these findings for how pattern-matching experts should present their evidence in reports and testimony and how courts should evaluate their weight and admissibility are discussed.