1. Pickel Investigating the effect of instructions to disregard inadmissible evidence.

2. Aims: To look at the effect of prior convictions. To look at the role of the judge’s instructions when they were followed by a legal explanation. To examine how much the credibility of the witness affects the juror’s ability to ignore inadmissible statements.

3. Methodology: An experiment using a mock trial of a fictional theft with a mock jury. The critical evidence was introduced ‘by accident’ by the witness. The item was objected by the attorney and then either allowed or overruled by the judge. In the former case, when jurors were instructed to ignore the inadmissible evidence, this ruling by the judge was sometimes supported by a legal explanation: that the inadmissible evidence might be suggestive of bad character in the defendant and so bias the jury. Sometimes no legal explanation was provided.

4. Participants: 236 Bali state university psychology students participated as part of a course requirement. They were assigned randomly to one of the conditions in an independent measures design.

5. Procedure: On arrival, participants listened to an audiotape of the trial and then completed an questionnaire asking them to make several decisions about the case. One was the verdict, the second was their estimate of the probable guilt of the defendant, and the third was a rating on a 10-point scale of the extent to which knowledge of the prior conviction caused them to believe the defendant was guilty. Finally they gave a rating on the credibility of each witness. There was a control group who did not get the critical evidence.

6. Results: As can be seen in the table (next slide), witness confidence is the only statistically significant effect of these listed variables under the conditions of the mock trial (all of the other six variables not shown were virtually identical).

7. Results table:

8. Results continued... In a further 9 studies, Cutler et al. Looked at the relation between confidence and accuracy. The correlations across the 9 studies between the two variables were 0.00 to 0.20, which is very weak indeed.

9. Conclusion: The evidence in the field is consistent in showing that confidence is a poor predictor of witness accuracy. It also shows that jurors’ trust in it is undiminished, even if the judge advises the jury to be wary of it in their summing up.