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Expert Scientific Testimony in Rape Trials

NCJ Number
105495
Author(s)
N C Brekke
Date Published
1985
Length
233 pages
Annotation
This study examines the effects of polygraph evidence, rape-trauma-syndrome evidence, and the presence or absence of opposing expert testimony on jury decisionmaking in a simulated sexual assault trial.
Abstract
Five general hypotheses were derived from the literature: jurors will give undue weight to the expert testimony; expert testimony will sidetrack the jury's attention from legally relevant issues; expert testimony will be prejudicial to the defendant; jurors will underuse evidence presented by an opposing expert; and juror confusion over conflicting evidence will produce a disregard for the testimony of both experts. A total of 906 undergraduates in introductory psychology classes at the University of Minnesota were tested on rape myth acceptance, perceived polygraph accuracy, perceived psychiatrist accuracy, and the predicted probability of rape based on rape trauma evidence and polygraph evidence. Subjects who completed the questionnaire were then asked to participate in a study of jury decisionmaking. For the 137 subjects who agreed, type of expert testimony (polygraph and rape trauma syndrome) and number of expert witnesses (single expert and two experts) were varied in a 2 x 2 factorial design with a control group that heard no expert testimony. Five mock juries of approximately balanced sex composition were randomly assigned to each of the five cells of the design. The juries listened to an audiotaped re-enactment of a sexual assault trial, deliberated to a verdict with the rest of the jurors in their group, and completed a final questionnaire. On the whole, the hypotheses received scant support. 3 tables, 106 references, and appended study instruments.

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