Forensic - Reaching a Verdict


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Pennington & Hastie

Effect of Order of Testimony

Aim: Investigate wheather or not story order evidence summmaries are true causes of the final verdict and the extent to which story order affects confidence in jurors verdicts. 

Sample: 130 university students (paid) allocated to one of four conditions in roughly equal numbers

Procedure: Lab exp. P's listened to a tape recording of the stimulus trial and responded to written questions. They had to reach a verdict on a murder charge and rate thier confidence from 1-5 without interaction. Story order condition - evidence was arragned in it natural order. Witness order - evidence arranged in the order closest to the original trial.

Results: Story order is most persuasive and provides jurors with the most confidence

Conclusions: The case they chose for the defence may have been less plausable

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Aim: Investigate whether hearing about psychological research from an expert witness cast doubt upon the accuracy of eyewtiness testimony would affect a juror's decision.

Participants: 538 undergraduates

Procedure: Lab exp. P's viewed a videotaped mock trial of a robbery and individually completed a questionnaire asking for their verdict + a memory test and rating scales of how confident they were. The four variables were:

  • Witness Identifying Conditions (good or bad)
  • Witness cofidence (100% or 80%)
  • Form of testimony (descriptive or relied on quantitative data)
  • Expert opinion (opinion on the accuracy of testimony between 0-25)

Results: Memory recall was scored at 85%, so poor memory cannot be blamed for the results of the study. WIC good - more guilty verdicts + higher confidence. Witness confidence increased juror confidence if they had heard expert witness.

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Effect of Evidence Being Ruled Inadmissible

Aim: Look at the effect of prior convictions + look at the role of the judges instructions when they were followed by a legal explanation.

Participants: 256 psychology uni students, independent measures

Procedure: A mock trial of a fictional theft with a mock jury. Critical evidence introduced accidentally by the witnesses, which was either allowed, overruled by the judge, or overruled by the judge and followed up with a legal explanation. After listening to the audiotape P's completed a questionnaire about their verdict, the probable guilt, and the 10 point scale on the effect of knowledge of prior convictions.

Results: Mock jurors who heard the evidence ruled inadmissable (no explanation) were able to ignore it and found the defendant guilty, where as those who heard the explanation were less likely to find the defendant guilty as they were unable to ignore it. No evidence to suggest that the creditibility of the witness would effect the jurors ability to disregard the evidence.

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Attractiveness of the Defendant

Aim: To test the hypothesis that attractive defendants are less likely to be seen as guilty.

Participants: 71m's + 74fm's university students

Method: Lab independent measures experiment using a mock trial

Procedure: P's were given a case with an attached photograph f the victim and defendant which had previously been caterogrised as attractive or unattractive by a panel of nine judges. P's were also given a questionnaire asking them to rate the defendant and the victim on 11 bipolar scales e.g. dull-exciting

Results: Physically attractive defendents and victims were both rated positivly on other personality variables. Attractive defendant - 56% guilty. Unattractive defendant - 76% guilty. With no significant differences in gender. 

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Witness Confidence 

Aim: Examine several factors including confidence which jurors may consider when deciding on their verdict.

Participants: Undergraduates 

Procedure: Videotaped trial of a robbery was presented, and the witness said she was either 80 or 100% confident in the identification of the robber. Nine other variables, both high and low, were introduced into the film.

After the film they were asked to state whether they felt the robber was guilty or not

Results: Witness confidnece was the only variable which effected their decision. Witness confidence increased the likliness of the robber being found guilty. 

Conclusions: Confidence is a poor predictor of eye witness accuracy + jurors trust in confidence is undiminished. 

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Effect of Shields & Videotape on Children Giving Evidence

AIm: To find out if the use of protective shields and videotaped testimony increases likelihood of a guilty verdict. Investigate the effect of protective devices such as shields and videotapes. Credibility inflation (child's testimony is enhanced  / Credibility deflation (child is seen as fragile) 

Participants: 300 students - 100 in each condition (open court, screen, videotape)

Procedure: Participants watched one of the three versions of the 2 hour film, produced by a professional film crew of the case of alleged abuse of a single touch while the father was giving the child a bath. The judge read  a warning before the screen was used to not imply guilt based on the use of it.

Results: There was no significant difference between the 3 conditions which show that the protective devices have no effect on credibility inflaction/deflation. Big gender difference

58.6% female - guilty      38.6% male - guilty 

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Stages in Decision Making

The jury goes through the following stages:

Orientation period: relaxed open discussions which set the agenda and raise questions & explore facts.

Open confrontation: Fierce debate which focus on smaller details, and the jury explore different interpretations. Pressure on the minority to conform. 

Reconciliation: Attempts to smooth over conflicts and the jurys tension is released through humour. 

One problem with the study is that actual jury's cannot be studied, so it can only be assumed that these processes occur. 












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Majority Influence

Aim: Investigate the effect of conformity to a majority when the task is unambiguous such as the length of a line

Procedure: A naive particpant was asked a question to which several stooges of the experimenter had already clearly given the wrong answer to. In total there were 18 trials. The stooges answered correctly to the first 2, but then out of the next 16, the stooges gave 12 incorrect answers, which were the 12 critical trials.

Results: Individuals conformed in one out of three occasions (32% conformity rate) Majorities bigger than 3 make very little difference to conformity rate

Conclusions: Strong tendency to confrom to group pressure which may be due to 3 reasons 

  • o   Distortion of perception- think the wrong answers were right
  • o   Distortion of judgement- they felt doubt about the accuracy of their judgement and therefore yielded to the majority view
  • o   Distortion of action- they didn’t want to be ridiculed and therefore went along with the group.
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Minority Influence

AIm: Examine minority influence and compare the impact of consistent minority and an inconsistent minority on the views of the majority. 

Procedure: Female p's as they are more interested in colour identifying. Participants were given eye tests to ensure they were not colour blind. They were then shown 36 slides which were clearly different shades of blue using filters and asked to state the colour of each slide out loud. Confederates were consistent and answered green for each of the slides. In the second part of the experiment they were inconsistent and answered green 24 times, blue 12 times. There was also control groups with no confederates.

Results: Percentage of answers green - Control - 0.25%, Inconsistent - 1.25%, Consistent minority - 8.42% 

The minority influence is based on informational social influence, providing the majority with new ideas that cause them to re-examine their views. 

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