Forensic - Reaching A Verdict - Persuading A Jury

Aim: to investigate whether or not story evidence summaries are true cases of the final verdict decisions and the extent to which story order affects confidence in those decisions

Method: Lab experiment, second of two reported in this paper

Sample: 130 students from Northwestern Uni and Chicago Uni, paid for participation, hour-long experiment. Allocated to 1/4 conditions- roughly equal nos.

Procedure: listened to tape of stimulus trial, responded to written Q's, told to reach verdict on murder charge, rate confidence of decision on 5-point scale, 39 prosecution items and 39 defence items in story order, 39 prosecution items and 39 defence items in witness order. 

Key Results: Story order persuaded more jurors of guilt. Defence items in witness order more jurors found guilty; defence-story order, guilty rate drops 31%. greatest confidence expressed by those who heard prosecution or defence in story order.

COGNITIVE/PSYCHODYNAMIC

Evaluation Points:

• determinism vs. free will
• reductionism vs. holism 

Method issues:

• low in ecological validity
• ethnocentric - students paid for participation

useful applications when applied to court cases and how witnesses told to present testimony. helped understanding of human phenomenon.

ignores other human complexities - deterministic. low in ecological validity - pps cannot feel full arousal felt in courtroom situation

Aim: to investigate whether hearing from expert witness which casts doubt on the accuracy of eyewitness testimony would affect a jury's decision

Method: Lab experiment using videotaped mock trial 

Sample: 538 undergraduates given extra credit for introductory psychology course

Procedure: viewed videotape, answered questionnaire: verdict, memory test, confidence rating scale. IV's were: witnessing identifying conditions (poor-robber seen, weapon shown), witness confidence, form of testimony, expert opinion

Key Results: juror verdicts: when WIC good, more guilty verdicts, effect increased if witness had given descriptive testimony. juror memory: 85% pps correctly recalled-memory cannot be blamed for judgement. juror confidence: under good WIC, more confident effect stronger if heard expert witness and if witness 100% confident

Conclusions: expert testimony improved jurors knowledge & made them pay more attention to WIC

COGNITIVE/PSYCHODYNAMIC

Evaluation Points:

• determinism vs. free will
• reductionism vs. holism

Method issues:

• low in ecological validity 
• sample attrition - students given extra credit

useful applications when applied to court cases and how expert witnesses affect a jury. helped understanding of human phenomenon

ignores other human complexities - deterministic. low in ecological validity - pps cannot feel full arousal felt in courtroom situation

Aim: to look at the effect of prior convictions, the role of judges instructions and examine how the credibility of witness affects jury to ignore inadmissible evidence 

Sample: 236 Bali State Uni students-course requirement, assigned to a condition randomly, independent measures design

Method: experiments using mock trial of theft with mock jury, critical evidence introduced 'by accident', objected and overruled

Procedure: listened to tape of mock trial, completed questionnaire: verdict, estimate of probable guilt, rating on 10-point scale which knowledge of prior convictions caused to believe guilt, rating on credibility of each witness. control group who did not get critical evidence.

Key Results: mock jurors who heard CE ruled inadmissible. less likely to find def guilty-unable to disregard and explanation. received no explanation able to follow instructions and ignore evidence. no evidence found to support hypothesis that credibility of witness affect jurors ability to disregard IE. no significant effect on use of prior conviction evidence as measured by 10-point scale.

COGNITIVE/PSYCHODYNAMIC

Evaluation Points:

• determinism vs. free will
• reductionism vs. holism

Method issues:

• low in ecological validity 
• sample attrition - students given extra credit

useful applications when applied to court cases and how expert witnesses affect a jury. helped understanding of human phenomenon

ignores other human complexities - deterministic. low in ecological validity - pps cannot feel full arousal felt in courtroom situation