Tanford, S., & Cox, M. (1988). The effects of impeachment evidence and limiting instructions on individual and group decision making. Law and Human Behavior, 12, 477-496.
Two studies were conducted to investigate the effects of impeachment evidence in civil cases. According to the Federal Rules of Evidence, impeachment evidence can be used to judge defendant credibility, but not to infer bad character or harmful propensity. Jury-eligible subjects watched a realistic videotaped trial in which prior convictions for perjury and character evidence of honesty or dishonesty were manipulated. In Study 1, subjects provided individual judgments, and in Study 2, subjects engaged in group deliberations. Impeachment evidence did not strongly affect verdicts, and character evidence of honesty decreased liability only when limiting instructions were given. In both studies, however, the evidence produced legally permissible and impermissible inferences. Prior convictions reduced perceived credibility and increased inferences of negligent propensity. Evidence of dishonesty produced lower credibility ratings and negative character impressions. Credibility, character, and propensity assessments were all important in the verdict-reaching process, suggesting that juror’s decisions do not conform to the requirements of the Rules of Evidence.
No impact of defendant’s past conviction for perjury or dishonest character evidence on jury verdicts or recall of trial testimony.