Expert testimony and jury decision making: An empirical analysis

This experiment examines the influence of expert psychological testimony on juror decision making in eyewitness identification cases. Experienced jurors and undergraduate mock jurors viewed versions of a videotaped trial, rated the credibility of the eyewitness and the strength of the prosecution's and defense's cases, and rendered verdicts. In the absence of expert testimony jurors were insensitive to eyewitness evidence. Expert testimony improved juror sensitivity to eyewitness evidence without making them more skeptical about the accuracy of the eyewitness identification. Few differences emerged between the experienced jurors and undergraduate mock jurors.     

Effects of Prejudicial Pretrial Publicity From Physical and Witness Evidence on Mock Jurors' Decision Making1

The effects of prejudicial pretrial publicity (PTP) from physical and witness evidence on decisions made by trained and untrained mock jurors were compared. Mock jurors viewed a videotaped rape trial and participated in jury deliberations. Training consisted of completion of a university course on psychology and law. As expected, physical evidence PTP produced more guilty votes than witness or no PTP. Both types of PTP influenced untrained mock jurors' punishment preferences and perceptions of satisfaction and fairness, whereas trained mock jurors' opinions on these measures were unaffected by PTP. Deliberations of trained mock juries were more task‐oriented and focused on relevant evidence and legal issues than that of their untrained peers. Limitations of this mock jury study were discussed.     

Will jurors correct for evidence interdependence in their verdicts? It depends

Throughout an investigation, pieces of evidence are likely to contaminate one another, yet at trial jurors are expected to treat pieces of evidence as if they are independent. Are jurors able to understand potential evidence contamination? The present study showed mock jurors a videotaped trial simulation. Participants were randomly assigned to hear testimony regarding one piece of evidence, two pieces of independent evidence, or two pieces of interdependent evidence. The study tested the hypothesis that jurors who hear evidence that is interdependent will be just as likely to find the defendant guilty as jurors who hear about two pieces of independent evidence. When an eyewitness's identification was the uncontaminated piece of evidence, our hypothesis was supported. However, when the confession was the uncontaminated piece of evidence, jurors seemed to understand that one piece of evidence had been influenced by another and adjusted their beliefs about the defendant's guilt accordingly. This study supports the conclusion that jurors can sometimes identify and correct for evidence contamination in their perceptions of a defendant's guilt. Implications for reform support are discussed.     

The Effect of Acknowledging Mock Jurors' Feelings on Affective and Cognitive Biases: It Depends on the Sample

An intervention designed to correct affective and cognitive biases was tested in the context of a civil commitment hearing of a sexually violent predator. Potential differences between a college student mock jury sample and a more representative, juror venire sample in reaction to these bias correction interventions were explored. In the first of two experiments, undergraduate mock jurors (n = 130) demonstrated a leniency effect when the sex offender's attorney acknowledged jurors' emotional reactions and motivated them to thoughtfully weigh the evidence. The second experiment failed to replicate these findings with a more ecologically valid sample (n = 300). Several differences between samples were found: representative jurors, as opposed to undergraduates, were sensitive to differences between pure clinical and actuarial expert testimony; and measures of intrinsic cognitive effort predicted verdicts for undergraduates, but not for representative jurors. Copyright © 2011 John Wiley & Sons, Ltd.     

Juror Need for Cognition and Sensitivity to Methodological Flaws in Expert Evidence1

This study examined whether need for cognition (NC) moderated jurors' sensitivity to methodological flaws in expert evidence. Jurors read a sexual harassment trial summary in which the plaintiff's expert presented a study that varied in ecological validity, general acceptance, and internal validity. High NC jurors found the defendant liable more often and evaluated expert evidence quality more favorably when the expert's study was internally valid vs. missing a control group; low NC jurors did not. Ecological validity and general acceptance did not affect jurors' judgments. Ratings of expert and plaintiff credibility, plaintiff trustworthiness, and expert evidence quality were positively correlated with verdict. Theoretical implications for the scientific reasoning literature and practical implications for trials containing psychological science are discussed.     

Linkage Analysis as Evidence in Court: A Thematic Analysis of Mock Juror Deliberations

Linkage analysis has, albeit occasionally, been presented in courts across the world as evidence that a series of offences possess behavioural similarities and distinctiveness from other offences, meaning they have probably been committed by the same individual. It is therefore imperative to ascertain how linkage analysis is regarded by juries within the context of deliberations. Three groups of participants (N = 22) eligible for jury duty in England and Wales viewed a simulated rape and murder trial derived from an actual South African case. Linkage analysis formed the sole evidence against the defendant in the two later offences, although DNA matches and eyewitness identifications of the defendant were present in the two earlier offences. Participant deliberations were recorded and subjected to thematic analysis. Five themes were discovered: behavioural consistencies and inconsistencies, physical versus case linkage evidence, barriers to admissibility, potential uses of linkage analysis, and dependence of lay knowledge. Jurors' over‐reliance on erroneous lay knowledge contributed to their conclusion that linkage analysis is, at present, unrepresentative evidence that cannot independently indicate a defendant's culpability. However, participants believed that linkage analysis could be a useful tool within investigations and, with further research evidence, in court in England and Wales. Copyright © 2014 John Wiley & Sons, Ltd.     

Reaction of mock jurors to testimony of a court appointed expert

A study was conducted to assess the impact of court appointed experts on the judgments of mock jurors. A civil proceeding was adopted for the experiment. Mock jurors heard testimony about a plaintiff's injury in an automobile accident. In some conditions, medical testimony for the plaintiff and defendant was provided by experts hired by each side. In other conditions, a medical expert appointed by the court testified in addition to the two adversarial experts. In one of these conditions, the court expert sided with the plaintiff; in another, the expert sided with the defendant. The plaintiff in the case was always an individual. The defendant was sometimes a corporation and sometimes an individual. The results showed that mock jurors sided with the court appointed expert in every condition except when the expert favored a corporate defendant. The results were discussed in terms of heuristic processing of persuasive information.     

The Social Psychology of Jury Nullification: Predicting When Jurors Disobey the Law1

The United States judiciary assumes jurors obey the law as it is charged to them in the trial judge's instructions. This paper contends that jurors' comprehension of the law results from an active intelligence which makes available alternative decision rules giving rise to the power of juries to nullify instructions. To study the compliance assumption, we presented to mock jurors pattern jury instructions along with summaries of testimonies from a rape trial. Four times during the trial we administered to participants measures of their attributions of defendant responsibility, judgments about the legal elements of the case, and verdicts. Multiple regressions conducted with data from separate subsamples and with separate questionnaire administrations revealed that a) verdicts were based on attributions independent of the jury instructions, b) individual differences in life experiences predicted the degree to which decision makers used their attributions, and c) the more practiced participants were at applying the jury instructions the more heavily they weighed their own attributions and less heavily the judgments required by the law. We concluded that comprehension alone cannot predict the likelihood that jurors will comply with the law. Therefore, the assumption that jurors follow the law needs to be more carefully considered.     

An exploration of psychological and physical injury schemas in civil cases

Civil plaintiffs often seek compensation for their psychological injuries. Yet little is known about jurors' preconceived notions (or schemas) for a prospective plaintiff's pain and suffering. The present studies examined (a) whether jurors have psychological injury schemas (Studies 1 and 2), (b) whether their existence and development vary by the type of civil case (Studies 1 and 2) or its severity (Study 2), and (c) how psychological injury schemas compare with physical injury schemas on a number of theoretically and legally relevant judgments (e.g., injury severity, availability, and plaintiff credibility; Study 2). Study 1 (N = 233) presented undergraduate mock jurors with 2 negligence incidents (car accident and slip and fall) and 2 intentional tort incidents (sexual assault and kidnapping) and asked them to report the typical incident and injuries that would result from the defendant's conduct. Results supported the sparse existence of psychological injury schemas but found that they were more developed in the kidnapping and sexual assault incidents than in the car accident and slip and fall incidents. Study 2 (N = 288) additionally manipulated incident schema severity (mild vs. severe) while having participants separately report and rate their psychological and physical injury schemas on judgments of legal and theoretical interest. Results indicated that although mock jurors' psychological injury schemas contained fewer injuries than their physical injury schemas, the reported psychological injuries were rated as more severe than physical injuries. We discuss how schemas may underlie the disparate treatment of psychological and physical injuries by legal decision‐makers.     

The Effects of Opening Statements on Mock Jurors' Verdicts in a Simulated Criminal Trial1

Twenty-nine male and 37 female adults served as mock jurors in a simulated criminal trial in which the amount of preview offered in both the prosecution's and defense's opening statements was factorially varied. It was found that the effects upon verdicts of guilt of the amount of preview in either side's opening statement depended on that in the other side's opening statement. Extensive prosecution opening statements led to more guilty verdicts only when the de fense's opening statement was also extensive; when the defense's opening statement was brief, participants tended to find the defendant guilty regardless of the amount of preview in the prosecution's opening statement. Extensive opening statements from the defense led to more not-guilty verdicts only when the prosecution's opening statement was brief. Results from a series of mid-trial measures indicated that opening statements predisposed jurors to favor one side or the other very early in the trial, and that jurors tended to maintain this predisposition throughout the course of the trial. It was suggested that opening statements serve to create thematic frameworks which the jurors use to assist them in their processing of trial information. Implications for legal practice were also discussed.     

The admissibility of expert testimony regarding malingering and deception

This article discusses the legal admissibility of expert testimony and the ability of mental health professionals to detect malingering and deception among defendants. A legal analysis of the admissibility of expert testimony regarding malingering and deception in formal legal proceedings is presented. Some guidelines are provided to help mental health professionals and attorneys determine the admissibility of evidence they intend to introduce. Although psychologists and psychiatrists currently have a limited ability to identify accurately malingering and deception, expert testimony about the genuineness of a defendant's mental illness is likely to be held admissible for both practical and evidentiary reasons. In contrast, evidence about a witness' credibility is rarely admissible. In addition, psychologists are ethically obliged to recognize their limitations in making representations about their skills.     

Expert testimony in child sexual abuse cases: The effects of evidence,coherence and credentials on juror decision making

Psychological experts have been used increasingly to testify in child sexual abuse cases, yet little research has investigated what specific factors make experts effective. This study examined the potential effects that credentials, evidence strength and coherence may have on juror decision making. Sixty‐four mock jurors read cases of child sexual abuse, followed by experts' testimony and rated guilt of the defendant, effectiveness of the expert testimony and credibility of the victim. Evidence strength and coherence of the testimony affected all dependent variables, and the interaction was significant. Guilt ratings of the defendant were lower and the victim was rated as less credible when both evidence strength and coherence were low. The credentials of the expert, however, had negligible impact. These findings indicate that experts can be effective and impact jurors when testimony is either high in coherence or high in evidence. Copyright © 2009 John Wiley & Sons, Ltd.     

Reality check: A comparison of college students and a community sample of mock jurors in a simulated sexual violent predator civil commitment

Despite concerns about generalizability, past mock trial research has concluded that effects of sample (i.e., students versus representative mock jurors) are negligible. The current study was conducted to explore this conclusion within the conceptual framework of cognitive–experiential self‐theory (CEST). Through a mock civil commitment hearing of a sexually violent predator, responses of student (n = 138) and representative (n = 240) mock jurors were compared. Results revealed several important differences between samples: (a) the student sample scored higher on the rational processing measure (i.e., need for cognition); (b) students' verdicts were also significantly correlated to a measure of their cognitive processing style, an enduring personal characteristic related to the extent to which an individual engages in either effortful/effortless cognition; and (c) the representative sample was more punitive, was more persuaded by clinical expert testimony, and evidenced a greater gender effect in its decisions. Implications for jury decision‐making research are discussed. Copyright © 2009 John Wiley & Sons, Ltd.     

Jurors' Decisions in Trials of Battered Women Who Kill: The Role of Prior Beliefs and Expert Testimony1

The present research explored the influence of four factors on mock jurors' decisions in a homicide trial involving a battered woman who killed her abusive husband: (a) jurors' preexisting beliefs about wife abuse, (b) the presence of expert testimony on the battered woman syndrome, (c) jurors' beliefs in a just world, and (d) gender. Mock jurors listened to a trial involving a woman who had killed her abuser, which either contained expert testimony or did not, and then rendered various judgments about the case. Results indicated that those individuals who were more informed about the dynamics of abuse and those exposed to the expert testimony, compared to their respective counterparts, were more believing of the battered woman's account of what occurred. In general, weak believers in a just world were more lenient in their judgments, with verdicts of not guilty being associated with weaker beliefs in a just world than guilty verdicts. Weak believers in a just world also felt that the expert testimony applied more to the defendant than did strong believers. Finally, women who were weak believers in a just world were less likely to hold the defendant responsible for the events and to be more informed about the dynamics of abuse following the experiment.     

Influences of Destructive Personality Information on Decision Making1

This study examined the effects of information about a landlord's personality on juror judgments for a landlord-tenant civil trial. The personality information manipulated was specifically relevant to destructive acts. Alternative versions of witness testimony were used to describe a landlord either high or low on need for power. treating people as objects, and negative life themes. This information strongly influenced aspects of the schema for this case constructed by the individual mock jurors. Destructive personality information caused dislike of the landlord and lowered the credibility of his story. If the landlord treated people as objects, the credibility of the tenant's story and positive evaluations of the tenant increased. Juror judgments about relative fault were strongly shifted by destructive personality information. An empirical model for juror decisions indicated a dynamic interplay of story components and fault judgments.     

Juries,Gender, and Assault Weapons1

Firearms appearance can have psychological import in legal proceedings by keying aggressive ideations, impacting sentencing and gender‐based attributions. We presented mock jurors with a homeowner's defensive gun use. Reasonable arguments were for shooting or not in the scenario by the defendant. The firearm varied in type. Assault rifle use led to harsher legal outcomes than did other firearms. A female defendant was at more risk than a male. In the last experiment, a police shooting scenario was tested. In that case, the male officer was at more risk than the female officer when wielding the assault rifle. Weapons and gender interactions were, for the most part, congruent with social cognitive theories of attribution and weapons priming of aggressive ideation.