| Expert witness testimony by psychologists has been a frequently discussed issue in psycholegal literature. However, there have been a limited number of quantitative studies measuring the effects of various cross-examinations and witness response styles. The current investigation examined the efficacy of impeachment techniques based on: (a) prior inconsistent statements, (b) witness bias, (c) contradictory theoretical evidence, and (d) witness demeanor. The effects of witness response styles ("appropriate" versus "inappropriate") were also evaluated. Two hundred undergraduates completed a juror qualification questionnaire, read an overview of a civil trial in which an individual was suing for wrongful termination, and completed ratings regarding the expert witness, attorney, and damage awards. The hypothesis that an expert witness with a calm, confident, and courteous demeanor during impeachment attempts would be rated higher on credibility by mock jurors on the Expert Witness Rating Form than an expert witness who responded with a defensive, excited, and argumentative style was not supported. The hypothesis that different impeachment methods would have varying levels of effectiveness for reducing witness credibility was supported. The most effective impeachment technique was based on witness bias, followed by contradictory theoretical information, witness demeanor, and inconsistent statements. The relationships between attorney effectiveness and aggressiveness, expert witness credibility and the factors of the Expert Witness Rating Form were also examined. Finally, implications for counseling psychologists testifying as expert witnesses were discussed. |
