The effect of following best practice reporting recommendations on legal and community evaluations of forensic examiners reports.

Commentators have recommended that forensic scientists' reports contain various disclosures to facilitate comprehension. However, little research has explored whether following best practice recommendations for disclosure impacts on receivers' impressions of the evidence. We examined whether forensic science reports that are more compliant with these best practice recommendations reduced overvaluing of the evidence and sensitized legal and community decision-makers to evidence quality. Across three experiments, 240 legal practitioners/trainees and 566 community decision-makers were presented with a fingerprint or footwear report that was either compliant or non-compliant with best practice recommendations. Participants were then asked to make evaluations and decisions based on the report. We found mixed effects of report compliance. Report compliance affected community participant's evaluations of the persuasiveness of the evidence but had limited impact on the judgments of legal practitioners/trainees. When presented with compliant reports, we found that community participants regarded unknown reliability evidence as less reliable and less persuasive than high reliability evidence, suggesting disclosures helped reduce overvaluing of the evidence and create sensitivity to differences in evidence quality. These results suggest compliance with reporting recommendations does affect community impressions, while only minimally influencing legal impressions of forensic science evidence. The costs and/or benefits of this outcome require further examination.

On the interpretation of likelihood ratios in forensic science evidence: Presentation formats and the weak evidence effect.

Likelihood ratios are increasingly being adopted to convey expert evaluative opinions to courts. In the absence of appropriate databases, many of these likelihood ratios will include verbal rather than numerical estimates of the support offered by the analysis. However evidence suggests that verbal formulations of uncertainty are a less effective form of communication than equivalent numerical formulations. Moreover, when evidence strength is low a misinterpretation of the valence of the evidence - a "weak evidence effect" - has been found. We report the results of an experiment involving N=404 (student and online) participants who read a brief summary of a burglary trial containing expert testimony. The expert evidence was varied across conditions in terms of evidence strength (low or high) and presentation method (numerical, verbal, table or visual scale). Results suggest that of these presentation methods, numerical expressions produce belief-change and implicit likelihood ratios which were most commensurate with those intended by the expert and most resistant to the weak evidence effect. These findings raise questions about the extent to which low strength verbal evaluative opinions can be effectively communicated to decision makers at trial.