Shifting decision thresholds can undermine the probative value and legal utility of forensic pattern-matching evidence
Date
2023-10-02
Authors
Thompson, William C.
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National Academy of Sciences
Abstract
Forensic pattern analysis requires examiners to compare the patterns of items such as fingerprints or tool marks to assess whether they have a common source. This article uses signal detection theory to model examiners’ reported conclusions (e.g., identification, inconclusive, or exclusion), focusing on the connection between the examiner’s decision threshold and the probative value of the forensic evidence. It uses a Bayesian network model to explore how shifts in decision thresholds may affect rates and ratios of true and false convictions in a hypothetical legal system. It demonstrates that small shifts in decision thresholds, which may arise from contextual bias, can dramatically affect the value of forensic pattern-matching evidence and its utility in the legal system.
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This article is published as Thompson, William C. "Shifting decision thresholds can undermine the probative value and legal utility of forensic pattern-matching evidence." Proceedings of the National Academy of Sciences 120, no. 41 (2023): e2301844120. doi:10.1073/pnas.2301844120. © 2023 the Author(s). Posted with permission of CSAFE.
This open access article is distributed under Creative Commons Attribution License 4.0 (CC BY).
This open access article is distributed under Creative Commons Attribution License 4.0 (CC BY).