Eyewitness accuracy and confidence

In deciding the trustworthiness of eyewitness testimony, the U.S. judiciary employs as one of five criteria the witness' level of confidence demonstrated at the confrontation. A very recent laboratory study has shown that juror perceptions of witness confidence account for 50% of the variance in juror judgments as to witness accuracy. This strong faith in the adequacy of certainty as a predictor of accuracy is not at all supported by the present review of 43 separate assessments of the accuracy/confidence relation in eye- and earwitnesses. Statistical support is provided for the notion that the predictability of accuracy from overtly expressed confidence varies directly with the degree of optimality of information-processing conditions during encoding of the witnessed event, memory storage, and testing of the witness' memory. Low optimal conditions, those mitigating against the likelihood of highly reliable testimony, typically result in a zero correlation of confidence and accuracy. Using the arbitrary criterion of 70% or greater accuracy to define high optimal conditions, seven forensically relevant laboratory studies are identified, with six of them exhibiting significant positive correlations of confidence and accuracy. It is concluded, however, that no really clear criteria currently exist for distinguishing post hoc high from low optimal witnessing conditions in any particular real-life situation. Hence the judiciary should cease their reliance on witness confidence as an index of witness accuracy.