Are Juries Competent?
● Spencer (2007) argues that jury verdicts are incorrect in at least 12.5% of cases
● So can juries reach verdicts relying only on the evidence presented in court and
disregarding information that is not evidence>
● Juries do focus heavily on evidentiary strength when determining their verdicts (Devine
et al., 2001; Devine, 2012)
Extralegal Information on Decisions
● Extralegal Information: Irrelevant information about the defendant's background or
appearance, PTP, or anything else not directly relevant to the trial
○ Example: Unattractive defendants more likely to be found guilty (Gunnell & Ceci,
2010)
● We'll focus more on these when you discuss Biases in Jury decision-making
Liberation Hypothesis
● Why is it that evidentiary strength has the most influence on jury decision-making, but
extra-legal factors could have an influence?
● Liberation hypothesis: when evidence is ambiguous, jurors are "liberated" and allowed to
rely on their assumptions, sentiments, and biases (Kalven & Zeisel, 1966)
● Several studies have found support for this hypothesis (Devine et al., 2009; Gunnell &
Ceci, 2010)
Can Jurors Disregard Inadmissible Evidence?
● Inadmissible evidence: Evidence presented in court but is unrelated to the substance of
the case
● In general, judge's admonition to disregard inadmissible evidence is ineffective (Steblay
et al., 2006) and may backfire (Liberman & Arndt, 2000)
● Reactance theory: limits on freedom is seen as a threat, people often do the opposite of
what they are told if they feel their freedom is being threatened (Brehm & Brehm, 1981)
● Thought Suppression: individual consciously attempts to stop thinking about a particular
thought (Wegner, 1994)
Effects of Expert Testimony
● In general, jurors do not defer to experts but there is a small, reliable effect on jury
decisions (Vidmar, 2005)
● If jurors do not understand testimony, they generally ignore it of defer to other jurors
(Greene, 2009)
● However, jurors are not good at distinguishing reliable scientific evidence from junk
science (Levett & Kovera, 2008; McAuliff et al., 2009)
Understanding Instructions
● Overall, jurors show an inability to understand their instructions (Liberman, 2009)
● Why?
○ Because they use legal jargon
● Spencer (2007) argues that jury verdicts are incorrect in at least 12.5% of cases
● So can juries reach verdicts relying only on the evidence presented in court and
disregarding information that is not evidence>
● Juries do focus heavily on evidentiary strength when determining their verdicts (Devine
et al., 2001; Devine, 2012)
Extralegal Information on Decisions
● Extralegal Information: Irrelevant information about the defendant's background or
appearance, PTP, or anything else not directly relevant to the trial
○ Example: Unattractive defendants more likely to be found guilty (Gunnell & Ceci,
2010)
● We'll focus more on these when you discuss Biases in Jury decision-making
Liberation Hypothesis
● Why is it that evidentiary strength has the most influence on jury decision-making, but
extra-legal factors could have an influence?
● Liberation hypothesis: when evidence is ambiguous, jurors are "liberated" and allowed to
rely on their assumptions, sentiments, and biases (Kalven & Zeisel, 1966)
● Several studies have found support for this hypothesis (Devine et al., 2009; Gunnell &
Ceci, 2010)
Can Jurors Disregard Inadmissible Evidence?
● Inadmissible evidence: Evidence presented in court but is unrelated to the substance of
the case
● In general, judge's admonition to disregard inadmissible evidence is ineffective (Steblay
et al., 2006) and may backfire (Liberman & Arndt, 2000)
● Reactance theory: limits on freedom is seen as a threat, people often do the opposite of
what they are told if they feel their freedom is being threatened (Brehm & Brehm, 1981)
● Thought Suppression: individual consciously attempts to stop thinking about a particular
thought (Wegner, 1994)
Effects of Expert Testimony
● In general, jurors do not defer to experts but there is a small, reliable effect on jury
decisions (Vidmar, 2005)
● If jurors do not understand testimony, they generally ignore it of defer to other jurors
(Greene, 2009)
● However, jurors are not good at distinguishing reliable scientific evidence from junk
science (Levett & Kovera, 2008; McAuliff et al., 2009)
Understanding Instructions
● Overall, jurors show an inability to understand their instructions (Liberman, 2009)
● Why?
○ Because they use legal jargon
