Eyewitness accuracy and confidence: Can we infer anything about their relationship?

Abstract

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.

The role of estimator variables in eyewitness identification.

“…We argue that estimator variables do not appreciably affect the reliability of identifications made with a particular level of confidence (particularly high confidence), and we offer a signal-detection-based theory of eyewitness identification taken directly from the basic recognition memory literature to account for that surprising result. We offer this theory as an alternative to the "optimality hypothesis" (Deffenbacher, 1980(Deffenbacher, , 2008, which holds that confidence becomes less indicative of accuracy under suboptimal estimator variable conditions. Our signal-detection-based theory consists of a standard likelihood ratio model of recognition memory.…”

“…The proposal is that the confidence-accuracy correlation should vary directly with the optimality of those conditions (Deffenbacher, 1980). In other words, the correlation should be higher when (for example) exposure to the perpetrator is long, distance between the witness and perpetrator is short, and stress is low compared to when exposure to the perpetrator is short, distance between the witness and perpetrator is long, and stress is high.…”

Accounts of the confidence-accuracy relation in recognition memory

“…Bothwell, Deffenbacher, & Brigham, 1987;Deffenbacher, 1980). There are at least two possible (nonexclusive) reasons for this weak relation.…”

Eyewitness identification: Retrospective self-awareness and the accuracy–confidence correlation.

“…To date, various reviewers of the empirical literature have consistently reached the same fundamental conclusion: that although there are exceptions, the correlation is weak and nonsignificant. Put another way, it appears that as a general rule, eyewitnesses who accurately and inaccurately identify a suspect from a photospread or lineup express equivalent levels of certainty in their respective judgments (Deffenbacher, 1980;Leippe, 1980;Wells & Murray, 1983, 1984.…”