Forensic psychology: Reaching a verdict

persuading a jury, witness appeal, reaching a verdict

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Pennington & Hastie

Aim

Method

Participants

Procedure

Results

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  • 1988
  • aim: investigate whether or not story evidence are true causes of final verdict decisions and extent to which story order affects confidence in these decisions
  • method: lab experiment
  • pps: 130 students from america who were paid
  • procedure: pps listened to tape recording of stimulus trial then did questionnaire
  • had to reach a verdict on the murder charge then rate their confidence 1-5
  • serperated by partitions and didnt interact with eachother
  • story-order condition - evidence arranged in its natural order
  • witness-order condition - evidence items arranged in order closest to original trial
  • 39 pieces of not-guilt evidence and 39 pieces of guilty evidence
  • results: story-order persuaded more to make guilty verdict in prosecution case
  • if defence was also witness-order the guilty verdict was even higher
  • positions reversed and defence had story-order guilty rate drops to 31%
  • greatest confidence shown by story-order condition prosecution and defence
  • least confidence in witness-order condition
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Pennington and Hastie (1988) Evaluation

  • primacy and recency effect controlled for
  • useful - lawyers can use story order to improve their chances of getting the verdict they want
  • lab experiment - high control, low ecological validity (video of trial, pps could confer)
  • pps - students (not representative of general population)
  • ethnocentric (american)
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Cutler et al

Aim

Method

Participants

Procedure

Results

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  • 1989
  • aim: whether hearing about psychological research from an expert witness which casts doubt on the accuracy of eyewitness testimony would affect a jurors decision making by making them more sceptical about such testimony
  • method: lab experiment using a videotaped mock trial
  • pps: 538 undergraduates given extra credit for into psychology course
  • procedure: pps viewed videotaped robbery trial in group of 2-8 and did a questionnaire with, verdict, memory test and rating scales for confidence
  • IV: witnessing identifying conditions - poor or good
  • witness confidence - 80% or 100%
  • form of testimony - descriptive or quantitative using percentages
  • expert opinion - half of trials expert expressed his opinion 0-25. decisions correlated with poor or good conditions in WIC
  • results: when WIC good more guilty verdicts given as well as when expert gave descriptive testimony. all other variables were less or insignificant
  • juror memory - 85% correctly recalled testimony, 50% recalled the four stages of memory and 81% recalled at least one stage
  • juror confidence - had more confidence in good WIC. effect stronger if heard the expert witness and if witness was 100% confident
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Cutler et al (1989) evaluation

  • lab experiment - high control, low ecological validity (videotaped mock trial)
  • pps - psychology students - more motivated, more likely to respect an expert witnesses opinion + to have read about the psychological research
  • useful - expert testimony improved jurors knowledge and made them pay more attention to WIC so may help prevent miscarriages of justice
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Pickel

Date

Aim

Method

Participants

Procedure

Results

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  • 1995
  • aim: look at effect of prior convictions, role of judges instructions when followed by a legal explanation and to examine how much credibility of witness affects the jurors ability to ignore inadmissable statements
  • method: experiment using mock trial of a fictional theft with a mock jury. critical evidence introduced by accident by the witness. item objected to and then either allowed or overruled by the judge. when jurors asked to ignore evidence the judge would sometimes support this with a legal explanation
  • pps: 236 psychology students particpating as part of course requirement
  • procedure: pps listened to audiotape of trial and completed questionnaire on the verdict, estimate of probably guilt of defendent, rating 1-10 of extent to which knowledge of prior convictions caused them to believe defendent was guilty, rating on credibility of each witness. control group didnt get the critical evidence
  • results: mock jurors who heard critical evidence ruled inadmissable and recieved no explanation were able to ignore the evidence
  • those who heard it ruled inadmissable and received an explanation were less likely to find defendent guilty and werent able to disregard it
  • no evidence that credibility of wtiness affected jurors ability to diregard evidence
  • no sig effect on use of prior conviction evidence as measured by 10 point scale
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Pickel (1995) evaluation

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  • psychology students - not representative, more motivated to take part
  • low ecological validity - audiotape of mock trial
  • self report - social desirability - may have lied about how much past convictions influenced them because they had been told to ignore it
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Castellow et al

Date

Aim

Method

Participants

Procedure

Results

11 of 33

  • 1990
  • aim: see if attractive defendant is less likely to be seen as guilty and if victim is attractive the defendant is more likely to be found guilty and if there are any gender differences in jury verdicts
  • method: lab experiment using mock trial
  • pps: 71m 74f students from america for extra credit in their intro psychology class
  • procedure: pps told theyd read a sexual harrassment case and have to answer questions on it. photographs of victim and defendent attached to case who had previously been categorised as attractive or unattractive by panel on scale of 1-9
  • had to make verdict and rate defendant and victim on 11 bipolar scales e.g. warm-cold
  • results: physically attractive defendant and victims rated positively on other personality variables as well
  • when defendant attractive guilty verdicts - 56% and for unattractive defendant 76%
  • when victim attractive guilty verdict = 77% and unattractive victim 55%
  • no significant gender differences found and both sexes equally influenced by appearance
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Castellow et al (1990) evaluation

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  • pps - psychology students from america - not representative, ethnocentric, may know about the halo effect which would influence their results, gender balanced
  • mock trial - low ecological validity
  • sexual harrassment - attractiveness is more likely to effect this type of case because you wouldnt expect an attractive man to sexually harrass an unnattractive person. other crimes such as theft may therefore not be as effected by attractiveness
  • useful - defendants would be advised to make the best of their appearance when in court to reduce their chances of getting a guilty verdict
  • lab experiment - high control
  • ethics - rating people as attractive or unattractive without consent
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Penrod and Cutler

Date

Aim

Method

Participants

Procedure

Results

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  • 1995
  • aim: whether witness confidence effects jurors assessment of eyewitness evidence
  • method: experiment using mock trial
  • participants: undergraduates, eligible and expererienced jurors
  • procedure: videotaped trial of robbery presented in which eyewitness identification played key role.
  • witness testified she was 80% or 100% confident she had identified the robber
  • 9 other variables at low/high lvl introduced into the film.
  • pps experienced either low or high condition variables on random basis and after watching film asked to decide whether robber was guilty or not
  • results: witness confidence was the only statistically significant effect, 100% had 67% convictions and 80% had 60% convictions
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Penrod and Cutler (1995) Evaluation

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  • video of mock trial - low ecological validity
  • pps - undergraduates - higher intelligence than average
  • independent measures - individual differences
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Ross et al

Date

Aim

Method

Participants

Procedure

Results

19 of 33

  • 1994
  • aim: find out if use of protective shields and videotaped testimony increases likelihood of guilty verdict and investigate the effect of protective devices on jury reaction to testimony - credibility inflation or deflation?
  • method: mock trial based on actual court transcript
  • pps: 300 college students (15m 150f) frim intro psychology course, majority white middle class. told it was a study of psychology and the law.
  • procedure: pps watched one of 3 versions of 2 hour film of court case of alleged abuse of a child by its father (open court/behind screen/video link)
  • abuse was a single touch whilst father giving child a bath = innocent/sexual?
  • judge read a warning before either screen/monitor used directy jury not to imply guilt by their use
  • pps then had to give verdicts and rate credibility of the child witness and defendant
  • results: guilty verdicts showed no significant difference between conditions
  • significant difference between male and female pps - 58.6% females found defendant guilty compared to 38.6% males
  • jurys perception of credibility of defendant & child didnt differ across 3 conditions although females rated defendant less credible and child more credible
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Ross et al (1994) evaluation

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  • mock trial - less arousal
  • pps - gender balanced, all psychology students
  • ethnocentric - majority white
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Hastie

date

what are the three stages and what does each stage involve?

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  • 1983
  • theory of stages and influences on decision making
  • jury discusion goes through 3 stages -
  • orientation period - relaxed and open discussion, set the agenda, raise questions
  • and explore facts, different opinions arise
  • open confrontation - fierce debate, focus on detail, explore different interpretations,
  • pressure on minority to conform, support for group decision made
  • reconciliation - attempts to smooth over conflicts
  • tension released through humour
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Hastie et al (1983) Evaluation

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  • actual juries cant be studied for legal reasons
  • its an assumption that these processes apply
  • need to question whether special nature of being locked in a room until you come to a unanimous decision means that this research needs to be applied with caution
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Asch

Date

Aim

Method

Participants

Procedure

Results

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  • 1955
  • aim: investigate effects of conformity to a majority when task is unambiguous
  • method: lab experiment
  • procedure: naive participant asked a question to which several stooges would give obviously wrong answers (which of the lines A B or C matches line X)
  • results: individuals conformed in 1/3 of occasions.
  • when 1 stooge gave the correct answer conformity fell to 5%
  • majorities bigger than 3 make little difference to the conformity effect
  • discussion: conform to majorities because of the need to belong to a group or the need to be right
  • need to be belong = part of socialisation process which particularly influences those with poorer self-esteem and is linked to a conformist personality
  • need to be right = when ambiguous situation occurs and we look to others solutions to guide our own
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  • lab experiment - low ecological validity (in a real jury the task is more complex so an individual juror may be more influenced to make the right decision and give the correct verdict especially if someones life is dependant on their decision
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Nemeth and Wachtler

Date

Aim

Method

Participants

Procedure

Results

30 of 33

  • 1974
  • aim: lab experiment of mock trial
  • pps: groups of 5 pps (one is a stooge) drawn from an adult sample of students
  • procedure: group of 5 had to deliberate on the amount of compensation due for a victim of an injury.
  • after hearing the facts everyone makes an individual verdict and is taken to another room where theres a rectangular table with 2 seats at the side and 1 at the head.
  • in half of the groups pps asked to sit at table with stooge choosing the head
  • in other groups the experimentor tells everyone where to sit
  • stooge takes a deviant position suggesting $3000 compensation instead of $10000-$25000 which was the view of the rest
  • results: confederate exerts influence when consistent & percieved as autonomous
  • when seated by experimentor he had little influence (measured by difference between original verdicts and later group ones)
  • when stooge has been influential this continues into the second case
  • when stooge sits at head of the table hes seen as more consistent and confident
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Nemeth and Wachtler (1974) Evaluation

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  • mock trial - in real jury the minority effect may be weakened by the need for unanimity in a limited time
  • students - not representative
  • lab experiment - high control, low ecological validity
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