The effects of rational and experiential information processing of expert testimony in death penalty cases

Past research examining the effects of actuarial and clinical expert testimony on defendants' dangerousness in Texas death penalty sentencing has found that jurors are more influenced by less scientific pure clinical expert testimony and less influenced by more scientific actuarial expert testimony (Krauss & Lee, 2003; Krauss & Sales, 2001). By applying cognitive-experiential self-theory (CEST) to juror decision-making, the present study was undertaken in an attempt to offer a theoretical rationale for these findings. Based on past CEST research, 163 mock jurors were either directed into a rational mode or experiential mode of processing. Consistent with CEST and inconsistent with previous research using the same stimulus materials, results demonstrate that jurors in a rational mode of processing more heavily weighted actuarial expert testimony in their dangerousness assessments, while those jurors in the experiential condition were more influenced by clinical expert testimony. The policy implications of these findings are discussed.     

The effects of labelling,expert testimony,and information processing mode on juror decisions in SVP civil commitment trials

Expert witnesses offering testimony in sexually violent predator civil commitment trials may use diagnostic labels that are either familiar (e.g. ‘psychopath’) or unfamiliar (e.g. ‘paraphilia’) to jurors. Using predictions based on cognitive experiential self-theory, we explored the influence of testimony type (clinical versus actuarial) and diagnostic label (psychopath versus paraphilia) on jurors motivated to adopt either an experiential processing mode (PM; in which heuristic cues may be strongly relied upon) or an analytic rational PM. Consistent with previous research, our results indicated that when given a psychopathic diagnostic label, mock jurors motivated to process information experientially were more influenced by clinical testimony, whereas mock jurors induced into a rational mode were more influenced by actuarial testimony. However, experientially oriented jurors given a paraphilia diagnostic label did not show the expected influence of clinical expert testimony, and instead were more persuaded by actuarial testimony. These findings are discussed from a judgement and heuristics cues framework. The implications of several procedural suggestions are examined. Copyright © 2009 John Wiley & Sons, Ltd.     

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 decision-making in a mock sexually violent predator trial: gender differences in the impact of divergent types of expert testimony

Despite widespread use of mental health testimony in cases where violence risk is at issue, relatively little is known about the impact of such information on juror decision-making. This study addressed the effects of testimony based on three types of risk assessment instrument or method (clinical opinion, actuarial assessment, and ratings of psychopathy) to examine whether they would have differential impact on jurors' perceptions of the defendant. In a mock sexually violent predator civil commitment trial, 172 undergraduates were presented a case summary that included prosecution and defense expert testimony related to violence risk based on one of the three methods noted above. Consistent with earlier research, the hypothesis that a defendant described as a "high risk psychopath" by the prosecution would be judged more severely than a defendant judged as "high risk" based on other evaluation procedures was supported, but only among female jurors. Unlike prior studies, little support was found for the hypothesis that clinical opinion testimony would be more influential than actuarially based testimony for either gender. Mechanisms that may underlie the observed gender differences are discussed, as are the potential implications of these findings for civil commitment proceedings.     

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.     

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 cognitive effects of jury aids on decision‐making in complex civil litigation

Two hundred seventy nine individuals served as mock jury members in a civil trial that involved multiple plaintiffs and several expert witnesses. Juries were or were not provided with written summary statements of the testimony of expert scientific witnesses, and were either permitted or not permitted to take notes. The results showed that the combination of summary statements and note‐taking had a synergistic effect on the quality of decision‐making. Mock juries enabled by both cognitive aids provided significantly higher awards, as compared to mock juries aided by one or none of the jury‐aids, to the most severely injured plaintiffs without increasing compensation for those less worthy. Aided mock juries also recalled more probative evidence than non‐aided jurors, and were more satisfied with the efficacy of their deliberations. Copyright © 2005 John Wiley & Sons, Ltd.     

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.     

Trivial persuasion in the courtroom: the power of (a few) minor details

Investigated the influence of trivial testimonial detail on judgments of 424 undergraduates who served as mock jurors. Ss read a summary of a court case involving robbery and murder. In Experiment 1, detailed testimony influenced judgments of guilt, even when the detail was unrelated to the culprit. In Experiment 2, detailed testimony was especially powerful when an opposing witness testified that she could not remember the trivial details. Subsequent analyses suggest that the impact of detailed testimony on guilt judgments is mediated by inferences about the eyewitnesses. When eyewitnesses provided more detail, they were generally judged to be more credible, to have a better memory for the culprit's face and for details, and to have paid more attention to the culprit.     

Jurors Report that Risk Measure Scores Matter in Sexually Violent Predator Trials,but that Other Factors Matter More

After deliberating to a verdict, jurors (N = 462) from 40 sexually violent predator (SVP) trials completed a questionnaire asking them to rate the extent to which risk measure scores, diagnoses, expert witness testimony, and offender characteristics described during the trials influenced their commitment decisions. Jurors reported that offenders' sexual offending history, failure to change, and lack of remorse had the strongest influence on their commitment decisions. They reported that testimony about risk instrument scores (e.g., Static-99) and psychopathy had less influence on their decisions, but those who did report being influenced by instrument results were especially likely to view the offender as being at a high risk for reoffending. Overall, findings suggest that SVP jurors view risk measure results as important, but not as important as other offender, offense, and testimony characteristics, including some that have limited relevance to recidivism risk. Thus, findings also suggest that experts may need to better educate jurors regarding factors that do and do not relate to recidivism risk. Copyright © 2015 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.     

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.     

Replications and Limitations of a Two-Factor Model of Child Witness Credibility

Two experiments are reported that test the idea that jurors perceive child witnesses in terms of a 2-factor model of credibility with the factors defined as cognitive ability and honesty (Leippe & Romanczyk, 1987; Ross, Millers, & Moran, 1989). In the first experiment, 300 mock jurors watched a realistic videotaped recreation of a sexual abuse trial and rated the credibility of the child witness. Mock jurors perceived the child witness in terms of 2 factors: cognitive ability and honesty. Only honesty predicted verdict. These findings were replicated in Experiment 2 ( N = 300) when only the child's testimony was presented and the perceptions of the child witness were not contaminated by the testimony of the other witnesses in the trial.