Dateline: March, 2011, Issue 4
Jurors often receive instructions limiting the use of particular evidence offered at trial.
Wissler and Saks (1985) investigated whether jurors are able to follow limiting instructions about a defendant's prior conviction. One group of jurors heard that the defendant had a prior conviction for a crime similar to that which the defendant was currently accused. A second group of jurors heard that the defendant had a prior conviction for a dissimilar crime. A third group of jurors heard that the defendant had a prior conviction for perjury. A fourth group of jurors did not hear any evidence of a prior conviction. All jurors presented with a prior record were instructed to use the prior record only to assess the credibility of the defendant's testimony and not as evidence of criminal disposition or character.
In complete opposition to the limiting instructions, the defendant's credibility was not affected by the prior record evidence, but verdicts were. The percentage of jurors voting to convict was higher when jurors learned the defendant had a prior conviction for a similar crime (75%), perjury (60%) or a dissimilar crime (53%) than when jurors were not told anything about a prior record (43%).
In a different study, Thompson and colleagues (1981) found that limiting instructions had their intended influence on the interpretation of evidence when the evidence favored the defense, but not when the evidence favored the prosecution.
When jurors are instructed that evidence is admitted for limited purposes, jurors use the evidence in that limited manner when the evidence is advantageous to the defense. When the evidence is disadvantageous to the defense, jurors use the evidence to determine guilt rather than only for its limited purpose.
Source Wissler, T. D., & Saks, M. J. (1985). On the inefficacy of limiting instructions: When jurors use prior conviction evidence to decide on guilt. Law and Human Behavior, 9, pp. 37-48.
Source Thompson, W. C., Fong, G. T., & Rosenhan, D. L. (1981). Inadmissible evidence and juror verdicts. Journal of Personality and Social Psychology, 40, pp. 453-463.