When forensic experts disagree: Examiner response patterns and aggregation rules in latent fingerprint examination

How should a laboratory combine opinions when examiners disagree about whether fingerprint evidence supports a definitive conclusion? We examine this question through an archival reanalysis of 17,121 responses from 169 examiners across 744 fingerprint pairs in the FBI latent-print Black Box Study. Comparison-stage inconclusive rates increased from 17.2% for comparisons rated obvious to 53.8% for those rated very difficult. A one-level increase in difficulty was associated with 1.58 times the odds of an inconclusive response after accounting for mating status and clustering by examiner and pair. Examiner inconclusive rates ranged from 5.7% to 81.2%, correlated across mated and non-mated comparisons (r = 0.61), and varied more than expected under pair-conditioned permutations. These patterns establish persistent response tendencies but do not separate perceptual ability from decision criteria. In exact retrospective calculations across 738 eligible fingerprint pairs, requiring a strict majority of all panelists reduced erroneous definitive conclusions from 3.80% for one examiner to 0.58% for seven. A majority taken only among definitive responses increased coverage but raised error to 9.88%, mainly through false exclusions. No-value and inconclusive responses remain distinct decision stages; they have the same voting effect only under the two rules examined. Larger absolute error reductions occurred on pairs with more dispersed responses, although the entropy measure does not distinguish uncertainty from contradictory conclusions. The findings illustrate how aggregation rules change error and coverage in a historical response distribution. They do not establish an optimal verification procedure or validate these rules for contemporary expanded conclusion scales.