For decades, researchers have found that jurors are consistently unable - or unwilling - to disregard inadmissible evidence when instructed to do so by a judge. The legal system ignores the problem entirely: judges have repeatedly affirmed that a judge’s instructions to disregard are a sufficient safeguard of defendants’ constitutional rights, regardless of whether the jury actually disregards the inadmissible evidence. This study tested four interventions derived from psychological research to identify the combination that most effectively helped jurors disregard inadmissible evidence (operationalized by lower conviction rates). It was hypothesized that the most effective interventions identified in Study 1 would yield significantly lower conviction rates when compared to traditional instructions to disregard in Study 2. The interventions were tested in Study 1 using Multiphase Optimization Strategy (MOST) methodology to identify the optimized intervention package through regression analysis. Study 2 served as a randomized controlled trial in which treatment as usual (a judge’s instructions to disregard) was compared to the optimized intervention package. Participants were randomly assigned to either (1) be exposed to no inadmissible evidence, (2) receive inadmissible evidence and treatment as usual, (3) receive inadmissible evidence, treatment as usual and the optimized intervention package, or (4) receive the inadmissible evidence without objection. Logistic regression revealed that jurors who were given an instruction to disregard produced lower conviction rates when they also received the optimized intervention package. Interpretation, limitations, and calls to action are discussed.

When questions about a person’s mental state arise in court, psychologists are often called in to help. Psychological assessment tools are routinely included in these evaluations to inform legal decision making. In accordance with the Daubert standard, which governs the admissibility of expert testimony, courts are obligated to exclude evidence that relies on poor scientific practice, including assessment tools. However, prior research demonstrates that psychological assessment tools with weak psychometric properties are routinely admitted in court, rarely challenged on the basis of their reliability, and if a challenge is indeed raised, often still admitted (Neal et al., 2019). Is neuropsychological assessment evidence in particular vulnerable to the same pitfalls? The present research aimed to 1) quantify the quality of neuropsychological assessment evidence used in court, 2) evaluate whether courts are calibrated to the quality of these tools through the rate and success of legal admissibility challenges raised, and 3) compare forensic mental health evaluators’ experiences and practices with regard to the quality of neuropsychological versus non-neuropsychological assessment tools. Neuropsychological tools appeared to perform worse than non-neuropsychological tools in terms of psychometric quality. However, in a case law analysis, significantly fewer challenges were observed to the legal admissibility of neuropsychological tools than to non-neuropsychological tools. To protect the legitimacy of the legal system and prevent wrongful decisions, it is critical that the evidence on which psychologists’ expert opinions are formed is scientifically valid, and that judges and attorneys adequately scrutinize the quality of evidence introduced in court.

Across three studies and two robust pilot studies, this project addressed issues surrounding prejudicial evidence and jury instructions to disregard inadmissible evidence. Specifically, this project examined a new framework for understanding how people vary in their response to prejudicial evidence, based on the morals they value, and tested the effectiveness of a novel way to phrase jury instructions to debias jurors inspired by moral foundations theory. In two experimental studies, participants read a transcript of a sexual assault (Study 1: n = 544) or an assault and battery criminal case (Study 2: n = 509). In each experiment, participants were randomly assigned to read either a case with or without prejudicial evidence. Participants exposed to prejudicial evidence were either given standard jury instructions to disregard the evidence, no instructions, or novel jury instructions inspired by moral foundations theory. Individual differences in moral foundations affected how susceptible people were to prejudicial evidence and case facts in general. This pattern emerged regardless of the type of jury instructions in most cases, suggesting that the moral foundation inspired instructions failed to help jurors disregard prejudicial evidence. The impact of people’s moral foundation endorsement has direct implications for how attorneys may phrase evidence to cater towards these moral biases and select ideal jurors during the voir dire process. To further advance people’s understanding of the effects of prejudicial evidence and jury instructions in legal settings, a third study looked at how attorneys (n = 138) perceived the prevalence and impact of prejudicial evidence in real cases and the effectiveness of jury instructions. Over three quarters of the sample (77.54%) reported having experienced prejudicial evidence in their cases and expressed concern that prejudicial evidence is influential to jurors with jury instructions being ineffective. Taken altogether, the results of this project show the potential impact moral foundation endorsement can have on case judgments and how jurors are differently influenced by prejudicial evidence. In addition, data from attorneys showing the perceived prevalent and impact of prejudicial evidence in real cases further justifies the need to continue researching safeguards against prejudicial evidence.

Cognitive heuristics, or mental shortcuts, sometimes give rise to biases that can influence decision making. These biases may be particularly impactful in a legal context where decision making has lifelong consequences. One such legal decision falls upon social workers who are often tasked with providing custodial recommendations in child custody cases. Across a series of 2 studies, I explored the role of confirmation bias in social worker decision making, the potential value of blinding to reduce bias, as well as social workers’ perceptions of their own biases. Social workers were given detailed case materials describing a custody case between the state and a father. Participants were randomly assigned to read a previous examiner’s positive evaluation of a father, a negative evaluation of the father, or were blinded to a previous examiners rating. Social workers engaged in confirmation bias, such that those who read a positive evaluation of the father viewed him more positively than participants who read a negative evaluation of the father, despite the fact that all of the actual case evidence remained constant. Blinding did not appear to mitigate the bias. In study 2, social workers viewed themselves as less biased than their peers and less biased than other experts in a different field – signifying the presence of a bias blindspot. Together, my findings suggest the need to further explore how bias might affect judgments and also how to mitigate biases, such as making experts aware of their potential for bias.

The United States Supreme Court’s 1993 Daubert v. Merrell Dow Pharmaceuticals case established criteria for admitting scientific evidence in federal courts. It holds that scientific evidence must be valid, reliable, and relevant, and judges are required to be “gatekeepers” of evidence by screening out evidence that has not been empirically tested or vetted through the academic community. Yet, little is known about whether psychological assessment tools are subjected to scrutiny through the standards courts are supposed to apply. In three different studies, from the perspectives of judges, attorneys, and forensic mental health experts, the authors investigate whether psychological assessment evidence is being challenged. Information was collected on participants’ experiences with challenges to psychological assessments. Judges and lawyers completed a series of experimental case vignettes to assess their decision-making about legal admissibility of different qualities of psychological assessments. It was hypothesized they would not distinguish between low- and high-quality psychological assessments in admissibility. Bayesian model selection methods did not support the null hypothesis, however. It was found attorneys differentiate between the conditions. The rates in which legal professionals and forensic mental health evaluators experienced challenges were also higher than was expected. These positive findings show there is some degree of gatekeeping psychological assessment evidence in the courts.

Biases have been studied in many legal contexts, including sexual assault cases. Sexual assault cases are complex because there are many stages that biases can come into play and have lasting effects on the rest of the case proceedings. One aspect that has not been widely explored is how people perceive institutions’ liability in sexual assault cases based on an obligation to create non-discriminating environments for members and employees according to laws like Title VII and Title IX. The current project focused on how and why cognitive biases affect laypeople’s judgment. Specifically, laypeople’s ability to discern the strength of evidence in civil sexual assault cases against institutions. This was addressed in a series of two studies, with samples collected from Prolific Academic (n = 90) and Arizona State University students (n = 188) for Study 1 (N = 278), and Prolific Academic in Study 2 (N = 449). Both studies used Latin-square design methods, with within and between subject elements, looking at how confirmation bias influenced decisions about whether an institution demonstrated negligence, and thus liability, in the way they responded to sexual assault allegations within their institution. Results from these studies suggest that jurors are overall accurately able to differentiate between weak and strong cases. However, consistent with previous literature, jurors may be susceptible to confirmation bias from outside information (e.g., news stories) and negatively influenced by their personal attitudes (e.g., rape myth acceptance). Given the increased attention of the Me Too movement, these results provide an initial insight into how individuals may be judging these types of cases against institutions.

This paper delineates two separate but related subfields of psychological science and practice applicable across all major areas of the field (e.g., clinical, counseling, developmental, social, cognitive, community). Forensic and correctional psychology are related by their historical roots, involvement in the justice system, and the shared population of people they study and serve. The practical and ethical contexts of these subfields is distinct from other areas of psychology – and from one another – with important implications for ecologically valid research and ethically sound practice. Forensic psychology is a subfield of psychology in which basic and applied psychological science or scientifically-oriented professional practice is applied to the law to help resolve legal, contractual, or administrative matters. Correctional psychology is a subfield of psychology in which basic and applied psychological science or scientifically-oriented professional practice is applied to the justice system to inform the classification, treatment, and management of offenders to reduce risk and improve public safety. There has been and continues to be great interest in both subfields – especially the potential for forensic and correctional psychological science to help resolve practical issues and questions in legal and justice settings. This paper traces the shared and separate developmental histories of these subfields, outlines their important distinctions and implications, and provides a common understanding and shared language for psychologists interested in applying their knowledge in forensic or correctional contexts.

This experiment uses the Community of Knowledge framework to better understand how jurors interpret new information (Sloman & Rabb, 2016). Participants learned of an ostensibly new scientific finding that was claimed to either be well-understood or not understood by experts. Despite including no additional information, expert understanding led participants to believe that they personally understood the phenomenon, with expert understanding acting as a cue for trustworthiness and believability. This effect was particularly pronounced with low-quality sources. These results are discussed in the context of how information is used by jurors in court, and the implications of the “Community of Knowledge” effect being used by expert witnesses.

Juror impartiality is necessary for a fair and just legal system, but is true juror impartiality

realistic? The current study investigated the role of implicit and explicit social-cognitive biases in jurors’ conceptualizations of insanity, and the influence of those biases in juror verdict decisions. It was hypothesized that by analyzing the role of implicit and explicit biases in insanity defense cases, jurors’ attitudes towards those with mental illnesses and attitudes towards the insanity defense would influence jurors’ final verdict decisions. Two hundred and two participants completed an online survey which included a trial vignette incorporating an insanity defense (adapted from Maeder et al., 2016), the Insanity Defense Attitude Scale (Skeem, Louden, & Evans, 2004), Community Attitudes Towards the Mentally Ill Scale (Taylor & Dear, 1981), and an Implicit Association Test (Greenwald et al., 1998). While implicit associations concerning mental illness and dangerousness were significantly related to mock jurors’ verdicts, they no longer were when explicit insanity defense attitudes were added to a more complex model including all measured attitudes and biases. Insanity defense attitudes were significantly related to jurors’ verdicts over and above attitudes about the mentally ill and implicit biases concerning the mentally ill. The potentially biasing impact of jurors’ insanity defense attitudes and the impact of implicit associations about the mentally ill in legal judgments are discussed.