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How do sex differences influence decision making?
- Women are significantly more likely to convict a defendant based on circumstantial evidence -Sealy & Cornish and were more than 20% more likely to judge defendants guilty in murder and rape cases (1973)
- Females change their initial verdicts more than males as further details emerge- Thomas (2010)
- Males deliver stiffer sanctions in mock trials Villemar & Hyde, and when a defendant is represented by a female they are significantly more likely to be acquitted (1983)
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How does race affect decision making?
- The higher the white:black ratio of a jury, the more likely a black defendant is given the death sentence in 340 cases (Bowers et al, 2001)
- White jurors more likely to vote guilty than black jurors, especially if the defendant was black in mock trials (Bernard, 1979)
- This extends to Latinos (Perez et al, 1993)
- Race didn't have a significant effect unless the case was ambiguous Ugwuegbu (1979)
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Why does race affect decision making?
- Superficial processing occurs and stereotypes have an effect
- People in the out group have evidence perceived in a different and more negative way
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What was the case of Vicky Pryce?
- Jury dismissed due to fundamental lack of understanding of legal proceedings
- Asked if they could use reasons not presented in court and with no evidential support
- Asked if they could speculate on the defendant's life and thoughts at the time of the offence
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How does legal jargon affect jury decision making?
- Liable to confuse jurors (Thomas, 2010)
- Jurors rated them as having significantly less understanding for difficult to follow instructions than easy ones
- The easiest instructions also yielded slightly lower understanding levels than slightly more difficult ones
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What is an expert witness?
- An individual qualified to offer an interpretation of the evidence
- To what extent can evidence from a crime scene be linked to the defendant of other sources
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What is the prosecutor fallacy?
- Use the example of the suspect's blood type matching that found at the crime scene (Elffers, 2012)
- Logical correct conclusion: a match is highly probable if it was the suspect who left the blood there
- Logical incorrect conclusion (the prosecutor's fallacy): A match indicates a high probability that the suspect left the blood
- This is untrue as there could be a large number of people in the population with this blood group
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How does conformity influence jury decision making?
- Asch (1951)
- We follow others when it conflicts with personally held values and beliefs
- Line length experiment, 75% agreed with wrong group answer
- More than 3 other needed for conformity and no dissenters
- Either normative (fit in with the group) or informational (believe others are right) social influence
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How has conformity been shown to affect decision making?
- Jury discussions strengthen majority position
- Nemeth (1983)
- P's asked to decide upon amount of compensation given in mock trial
- Confederate gives exceedingly low amount
- P's adjusted their estimations downwards after this
- This was more pronounced if the confederate sat at the head of the table
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What is the story model?
- Pennington & Hastie (1991)
- Jurors construct a causal and incentive based story in their mind to make sense of evidence
- Evidence is evaluated based on this story and is used to fill in the gaps and strengthen it
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How does the story model affect jury decision?
- Pennington % Hastie (1992)
- P's given a memory recognition task
- Remembered more sentences that were consistent with the story that led to their verdict than ones from stories associated with a different one
- Used mock jurors and presented evidence in either story or witness format
- P's significantly more likely to convict or acquit if the evidence is presented in story format
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What cognitive biases affect the judgements made by judges?
- Fitzmaurise & Pease (1986) found that:
- Ross & Nisbett (1990)- Judges are subject to fundamental attribution error, attributing internal characteristics to behaviour or evidence
- Judges experience the anchoring heuristic: placing undue weight on the first piece of information presented (Kahneman & Tversky 1974)
- Judges showed conformity effects and stubborn first impressions (confirmation bias, Watson, 1960) and Snyder & Swann (1978)(subsequent behaviour perceived in a biased way)
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How do judgments from judges and juries compare?
- Kalven & Zeisel (1966)
- Over 3500 US trials reviewed and guilty verdict from judge and jury compared using a questionnaire
- 78% concordance rate for convictions
- Greater tendency for jurors to acquit when a judge would convict than vise versa (19%/3%)
- Similar findings from Eisenberg et al (2003)
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Are biases exclusive to judges and juries?
- No- Kassin, Bogart & Kerner (2012)
- Looked at the effect of confirmation bias from false confessions on subsequent evidence gathering
- 78% of cases contained errors such as improper evidence gathering and interpretation of witnesses
- This was more pronounced if a confession was received first
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