An inconvenient truth: More rigorous and ecologically valid research is needed to properly understand cognitive bias in forensic decisions

Challenges to reasoning in forensic science decisions

The success of forensic science depends heavily on human reasoning abilities. Although we typically navigate our lives well using those abilities, decades of psychological science research shows that human reasoning is not always rational. In addition, forensic science often demands that its practitioners reason in non-natural ways. This article addresses how characteristics of human reasoning (either specific to an individual or in general) and characteristics of situations (either specific to a case or in general in a lab) can contribute to errors before, during, or after forensic analyses. In feature comparison judgments, such as fingerprints or firearms, a main challenge is to avoid biases from extraneous knowledge or arising from the comparison method itself. In causal and process judgments, for example fire scenes or pathology, a main challenge is to keep multiple potential hypotheses open as the investigation continues. Considering the contributions to forensic science judgments by persons, situations, and their interaction, reveals ways to develop procedures to decrease errors and improve accuracy.

Quality of Laypersons' Assessment of Forensically Relevant Stimuli

The current study examined the potential for cognitive bias in lay examiners' comparisons of footwear impressions within the technical review process while addressing limitations of previous research. Prior research has found inconsistent results regarding the extent to which cognitive bias may influence forensic comparisons, often asking non-experts to review forensic stimuli above their competency level. Furthermore, past research has largely ignored the potential for cognitive bias during the technical review process. In collaboration with the Miami-Dade Police Department's Forensic Services Bureau, we examined the effects of previous examiners' level of experience and prior knowledge of the previous examiner's decision on the technical review stage of footwear impression stimuli. Before lay examiners were presented with pairs of known match and nonmatch footwear impressions, they were either told that an expert or a novice had previously examined them and determined them to be either a match, nonmatch, or inconclusive (plus a no-information condition). Participants then evaluated each pair of footwear impressions to make their own determinations of match, nonmatch, or inconclusive. Results support the technical review process for all decision types, as known nonmatch stimuli were generally more difficult for lay examiners to assess than known match stimuli. Knowledge of a prior examiner's decision and status was observed only when the prior decision was inconclusive, suggesting the need for inclusion of inconclusive decisions in future research examining cognitive bias in forensic examination.