Cutler et al.<br />The effect of the expert witness on jury perception of eyewitness testimony.<br />
Aim<br />To investigate whether hearing about psychological research from an expert witness which casts doubt on the accuracy of eyewitness testimony would affect a juror’s decision-making by making them more sceptical abut such testimony. <br />
Methodology<br />A lab experiment using a videotaped mock trial. <br />
Participants<br />538 undergraduates who were given extra credits for their introductory psychology course. <br />
Procedure<br />Participants viewed a videotaped robbery trial in groups of 2 to 8. Afterwards, they independently completed a questionnaire containing the dependent measures these included: <br /> Verdict<br />A memory test.<br /> Rating scales for how confident they were. <br />
Continued...<br />There were 4 independent variables: <br />Witnessing Identifying Conditions (WIC) – whether the conditions were poor i.e. The robber was disguised, brandishing a handgun, there was 14-day delay in the identification of the robber by the witness and the line-up instructions were suggestive. Or the conditions were good – no disguise, a hidden gun, a 2-day delay in the identification and no suggestive instructions. <br />
2. Witness confidence– the witness testified that she was (a) 80% or (b) 100% confident that she had correctly identified the robber. <br />3. Form of testimony – whether the expert psychologist described the results of eyewitness research in a descriptive way (i.e small, medium or large effect.) or whether it was quantified using percentage of correct or incorrect identifications. <br />
4. Expert opinion– In half the trials the expert expressed his opinion on a scale from 0 (least likely to be correct) to 25 (most likely to be correct). These decisions coincided with the poor or good condition in variable 1. <br />
Results(Juror verdicts)<br />When the WIC were good, more guilty verdicts were given and this effect increased if the expert witness had given descriptive testimony. All other variables were less significant or insignificant. <br />
Results (Juror memory)<br />Of the participants 85% or more correctly recalled the testimony, so memory cannot be blamed for any lack of effect on jurors’ judgements. In addition, memory for what the expert had said was also good, 50+% recalled the four stages of memory (perception, encoding, storage and retrieval) 81% recalled at least one stage. They also recalled correctly what the expert had said about weapon effects, disguises and delays in identification. <br />
Results (Juror confidence)<br />Again it was under the good WIC that the jurors had more confidence in the accuracy of the identification. This effect was stronger if they had heard the expert witness and if the witness was 100% confident rather than 80% confident. <br />
Discussion<br />The experiment showed that the expert testimony improved jurors’ knowledge and made them pay more attention to WIC. It decreased the reliance on witness confidence alone and there was no evidence to suggest that expert testimony made the jury sceptical about the witness’s credibility, the accuracy of the identification or the defendants culpability. With expert testimony, juror sensitivity to problems with evidence is improved and may help to prevent miscarriages of justice. <br />
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