The legal system relies on voir dire to ensure the Sixth Amendment guarantee of an impartial jury. This dissertation tests the assumptions of voir dire that venire jurors 1.) can identify their biases accurately and 2.) will report them honestly. It was proposed that venire jurors would underreport their bias. As a result, we hypothesized that a significant proportion of venire jurors who claim that they are impartial would be inaccurate. The present study sought to disentangle whether the jurors are inaccurate because they are unaware of their bias or unwilling to admit it. First, it was hypothesized that increasing participant’s privacy during voir dire would increase their disclosures of bias. However, it was also hypothesized that increasing venire juror’s candidness would not increase the accuracy of their self-reports of bias. That is, we expected to find evidence that jurors underreport bias because they lack awareness of it.

The present study was conducted at the Orange County Superior Courthouse with 382 venire jurors. An anti-defendant bias was induced experimentally in a sample of the participants through exposure to pretrial publicity (PTP). The participants then completed a mock trial. During voir dire, participants were asked about their ability to be impartial. Participants exposed to PTP were randomly assigned to complete voir dire either through an in-person interview or a paper-and-pencil questionnaire. Then the participants read a case summary and rendered a verdict. Last, participants completed a post-verdict questionnaire assessing how they thought the PTP affected their verdict.

The data revealed that the majority of PTP-exposed venire jurors (70%) maintained that they were not biased. However, privacy did not influence their self-reports of bias, revealing no support for the hypothesis that venire jurors systematically underreport bias. Further, the findings did not support the hypothesis that venire jurors’ self-reports are inaccurate. Participants who said that they were biased were significantly more likely to convict (48%) compared to those who said that they were impartial (21%). Participant’s accuracy also did not vary as a function of their level of privacy during voir dire. Overall, these findings suggest that venire jurors can and do provide accurate self-reports of pretrial publicity bias.

Although research consistently reveals that children as young as three can use deception and will take steps to obscure truth, research concerning how well others detect children’s deceptive efforts remains unclear. Yet, adults regularly assess whether children are telling the truth in a variety of contexts, including school, home, and legal settings, particularly in investigations of maltreatment. We conducted a meta-analysis to synthesize extant research concerning adults’ ability to detect deceptive statements produced by children. We included 45 experiments involving 7,893 adult judges and 1,858 children. Overall, adults could accurately discriminate truths/lies at an average rate of 54.3%, which is significantly above chance levels. The average rate at which true statements were correctly classified as honest was higher (59.7%), while the rate at which false statements were classified as dishonest was at chance (49.4%). A small positive correlation emerged between judgment confidence and judgment accuracy. Professionals (e.g., social workers; police officers) slightly outperformed laypersons (e.g., college undergraduates). Finally, exploratory analyses revealed that the child’s age did not affect the rate at which adults could discriminate truths/lies but it was trending in the expected developmental direction (i.e., adults were most accurate when judging younger children).

With few exceptions, jurors in criminal trials exclusively determine whether the defendant is guilty; they do not determine what the sanction is or even recommend what it should be. However, anecdotal evidence suggests that jurors make assumptions regarding the potential punishment, and that these assumptions inform their verdicts. This is rational behavior according to Decision Theory. Thus, several legal scholars have argued that jurors ought to be informed of the possible punishment that would follow a guilty verdict, in order to disabuse incorrect assumptions and make an informed decision. The present experiments tested: a.) whether jurors do make assumptions about the potential punishment that would follow from a guilty verdict; b.) whether those assumptions influence jurors’ implicit threshold for reasonable doubt; and c.) whether informing jurors of the potential punishment additionally influences their implicit threshold.  Experiment 1 manipulated the alleged crime (Grand Theft vs. Manslaughter) holding all other factors constant, and found that mock jurors (n=102, recruited via Amazon Mechanical Turk) had different expectations about the relative punishments but that these expectations did not affect their implicit threshold for reasonable doubt. Experiment 2 manipulated the alleged crime as well as a judicial description of the potential punishment (e.g., term of incarceration of 2-6 vs 7-20 years). Again, mock jurors (n=297) were sensitive to the relative punishments, yet their implicit threshold did not differ on this basis. These findings call into question whether jurors should be informed of the potential punishment if the defendant is convicted.

The Supreme Court ruled in Atkins v. Virginia (2002) that intellectually disabled defendants cannot be sentenced to death. However, little is known about how intellectual disability judgments are made by jurors in capital cases. Our experiment addresses this gap by examining the impact of both clinical expert opinions and crime information on jurors’ disability judgments and death sentencing behavior. In a study of 286 venire jurors, we found that expert opinions significantly influenced juror disability decisions and death sentencing – with juror judgments tending to align with expert opinions – and exposure to crime details made jurors significantly more likely to sentence the defendant to death. Our results suggest that to protect the rights of disabled defendants, it may be necessary for courts to have a separate hearing on the issue of intellectual disability specifically – without crime details – to ensure jurors are not unduly influenced.

The Story Model of Juror Decision Making states that as jurors are exposed to new pieces of evidence, they continually integrate evidence into a “story” about what happened in the case; this process includes evaluating contradictory testimony and discounting evidence that does not fit within the juror’s narrative about the case. Existing research has neglected to test how forensic DNA evidence is incorporated into jurors’ narratives, especially if the DNA is inconsistent with the non-forensic evidence. The lack of emphasis on forensic evidence should be addressed given the perception of infallibility that surrounds DNA. Study 1 manipulated non-forensic evidence strength and whether there was a DNA match to test how jurors integrated DNA evidence into their narrative interpretation of the case. Results indicated that utilization of forensic testimony depended on the non-forensic evidence strength and reliance on non-forensic evidence depended on whether there was a DNA match. To expand the results from Study 1 and incorporate the possibility of error in DNA testing, Study 2 manipulated whether a DNA match did or did not contain laboratory error rate evidence and the strength of the non-forensic evidence to examine how jurors integrate error rates into their narrative about a case. Results showed that jurors were not sensitive to the laboratory error rates manipulation. Together, these studies indicate that jurors are not sensitive to the possibility of erroneous DNA results, but integrate DNA identifications into their narrative; this suggests that bias might be integrated into their narratives that facilitate false convictions.

Although extensive social psychological research has examined conformity for individualized behaviors, no laboratory research has experimentally manipulated conformity in the context of group decisions. Normative conformity is motivated by the desire for social acceptance while informational conformity entails looking to others for correct answers. Using the applied context of a jury deliberation, the present studies aimed to disentangle the relative effects of normative and informational conformity by comparing participants’ votes and ratings of evidence convincingness before and after exposure to a confederate group’s opinions during a poll. Private polls were intended to shield jurors from normative influence, while public polls invited conformity via both normative and informational influence. Results showed disagreement with the group majority during the first poll was a consistently strong predictor of vote switching, but no significant differences emerged in vote switching between public and private deliberation. Changes in beliefs about the strength of the evidence against the defendant partially mediated the effect of a disagreeing majority on vote switching. For participants who initially voted guilty, changes in beliefs drove a greater proportion of conformist vote switching in public deliberations than in private deliberations. This finding suggests that people may weigh public comments in group decisions more heavily or that the pressure to conform in public deliberation may increase susceptibility to belief change. More generally, it also suggests that normative pressure may sometimes fuel informational influence, and that the two constructs may be more linked than previously conceptualized. Implications are discussed for extant research on the intersection between conformity and group decision making and for jury protocol.

Informants are an integral part of the American criminal justice system. However, relatively little research has been done on nearly all aspects of informant use, from how they are recruited and how they reach agreements to cooperate with law enforcement to how jurors evaluate their testimony in court. The present study focuses on this last area – juror perceptions of informants who testify. The limited research that exists on this topic has presented troubling conclusions: jurors may not be appropriately responsive to cues that could signal informant unreliability. In particular, jurors may fail to account for and properly weigh evidence that an informant is testifying for an incentive (such as a reduced prison sentence) when reaching a verdict. However, thus far, studies in this area have some limitations in case type, materials used, and statistical power. The objective of the current study is to advance in each of these areas and provide new evidence about the impact of juror perceptions of informant incentives. This study used a novel fact pattern, video stimuli manipulations, and a sample of 886 online participants to test the impact of informant incentives on juror judgments. It featured four conditions that vary the nature and size of the incentive reported by a jailhouse informant (i.e., no incentive, a vague leniency incentive, and small and large sentence reduction incentives), plus a control condition with no informant testimony. The results speak to the conflicted literature on this topic – finding a significant impact of incentive presence on verdicts. Participants who observed an incentivized informant rated him as less credible and were less likely to convict the defendant based on his testimony – compared to participants who viewed an otherwise identical non-incentivized informant. However, participants’ verdicts in this study were not sensitive to changes in the size of an informant’s incentive, showing no significant difference in conviction rates when the incentive was large (10 years off of a 20-year sentence) compared to small (1 year off of a 20-year sentence). This study also included a test of a novel hope-for-leniency condition, which prompted verdict responses most similar to that of the small incentive condition. These results suggest that jurors may be more capable than previously thought at accounting for informant incentives in reaching a verdict. It also suggests that reforms that aim to preserve evidence of jailhouse informant incentives and ensure that such information is able to reach a jury at trial have potential to meaningfully influence verdict outcomes.