Polygraph Testimony and Juror Judgments: A Comparison of the Guilty Knowledge Test and the Control Question Test1

The present experiment investigated the impact of the Control Question Test (CQT) and the Guilty Knowledge Test (GKT) on the verdicts of mock jurors. Although studies have indicated that polygraph evidence has little influence on jurors' verdicts (Cavoukian & Heselgrave, 1980; Spanos, Myers, Dubreuil, & Pawlak, 1992–1993), no research has previously distinguished between the different types of polygraph tests and their impact on juror verdicts. In the present study, jurors were shown a videotape of a simulated rape-murder trial that contained either CQT polygraph evidence, GKT polygraph evidence, or no polygraph evidence. No differences were found among the 3 conditions for either jury verdicts or individual juror verdicts, and jurors tended to rate both forms of polygraph testimony below other forms of equally suspect evidence, such as eyewitness testimony, in its influence on their decision-making process.     

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.     

Undermining Reasonableness: Expert Testimony in a Case Involving a Battered Woman Who Kills

Student participants  ( N = 316)  viewed a videotaped simulated case involving a woman who had entered a self-defense plea in the shooting death of her abusive husband. As successful claims of self-defense rest on the portrayal of a defendant who has responded reasonably to his/her situation, the implications of various forms of expert testimony in constructing this narrative were examined. Jurors were presented with either expert testimony regarding the battered woman syndrome (BWS), the BWS framed within post-traumatic stress disorder (PTSD) nomenclature, or a no-expert control condition. As the BWS classification may support a stereotypical victim, the degree to which the defendant fit the stereotype in terms of her access to a social support network (family, friends, employment outside of the home) was varied within the expert testimony conditions to reflect either a high or low degree of stereotype fit. Although jury verdicts failed to differ across expert testimony and stereotype fit conditions, perceptions of her credibility and mental stability did. Although affording jurors a framework from which the defendant's experiences as a battered woman may be acknowledged, this portrayal, as advanced within PTSD nomenclature, endorsed a pathological characterization of the defendant. Implications of this discourse for battered women within the context of self-defense are discussed.     

The influence of FMRI lie detection evidence on juror decision-making

In the current study, we report on an experiment examining whether functional magnetic resonance imaging (fMRI) lie detection evidence would influence potential jurors' assessment of guilt in a criminal trial. Potential jurors (N = 330) read a vignette summarizing a trial, with some versions of the vignette including lie detection evidence indicating that the defendant was lying about having committed the crime. Lie detector evidence was based on evidence from the polygraph, fMRI (functional brain imaging), or thermal facial imaging. Results showed that fMRI lie detection evidence led to more guilty verdicts than lie detection evidence based on polygraph evidence, thermal facial imaging, or a control condition that did not include lie detection evidence. However, when the validity of the fMRI lie detection evidence was called into question on cross-examination, guilty verdicts were reduced to the level of the control condition. These results provide important information about the influence of lie detection evidence in legal settings. Copyright © 2011 John Wiley & Sons, Ltd.     

The Influence of Eyewitness Nonidentifications on Mock-Jurors' Judgments of a Court Case1

Two experiments examined the effect of an eyewitness nonidentificution on mock-jurors' verdicts in robbery cases, as well as the effects of number of identifying eyewitnesses and status of the identifying witness (victim or bystander). Subjects read court case summaries that included variable eyewitness evidence and constant alibi, circumstantial, and character evidence. In Experiment 1, frequency of guilty verdicts was significantly less when an eyewitness testified in court that the defendant was not the perpetrator, even when this nonidentification opposed two positive identifications. In Experiment 2, a low guilty rate was again associated with the presence of a nonidentifier, but only when the nonidentifier actually testified in court and stipulated that the defendant is “not the man.” On the average, 70% of the jurors delivered guilty verdicts when both the victim and bystander gave identifying testimony, whereas 12.5% delivered guilty verdicts when the bystander gave opposing nonidentifying testimony. Guilty rates were unaffected by the identifying eyewitness' status and (in Experiment 2, but not Experiment 1) were higher when there were two (vs. one) identifying eyewitnesses.     

How the Defendant's Emotion Level Affects Mock Jurors' Decisions When Presentation Mode and Evidence Strength Are Varied1

Two experiments (N= 443) were conducted to investigate the effects of a defendant's emotion level during testimony on mock jurors' decisions. In Experiment 1, the defendant's level of emotion (low, moderate, high) and mode of presentation (audio, video) were varied. The defendant displaying a low level, as opposed to a higher level of emotion was perceived as more guilty and less credible. In Experiment 2, using only the video mode, emotion level and evidence strength (strong, weak) were varied. Defendant emotion level tended to affect jurors' decisions only when the evidence against the defendant was weak (i.e., a stronger display of emotion was associated with a lower proportion of guilty verdicts, shorter sentence assignments, and perceptions of a more honest defendant). Path analyses for both experiments indicate that the effects of emotion on perceived guilt level are mediated by perceptions of the defendant (e.g., the defendant's level of honesty). Implications of using defendant emotion level for determining guilt are discussed.     

How effective are the cross-examination and expert testimony safeguards? Jurors' perceptions of the suggestiveness and fairness of biased lineup procedures

Mock jurors (N = 800) viewed a videotaped trial that included information about a lineup identification procedure. Suggestiveness of the eyewitness identification procedure varied in terms of foil, instruction, and presentation biases. Expert testimony regarding the factors that influence lineup suggestiveness was also manipulated. Criteria included juror ratings of lineup suggestiveness and fairness, ratings of defendant culpability, and verdicts. Jurors were sensitive to foil bias but only minimally sensitive to instruction and presentation biases. Expert testimony enhanced juror sensitivity only to instruction bias. These results have implications for the effectiveness of cross-examination and expert testimony as safeguards against erroneous convictions resulting from mistaken identifications.     

Sensitizing Potential Jurors to Variations in Eyewitness Evidence Quality Using Counterfactual Thinking

Jurors often have difficulty evaluating eyewitness testimony. Counterfactual thinking is a type of mental simulation that informs causal inference. Encouraging jurors to think counterfactually about eyewitness factors may sensitize them to these factors' causal influence on eyewitness identification and testimony accuracy, improving their overall judgments (such as verdicts). One hundred twenty‐one undergraduate participants were randomly assigned to read a scenario containing either high‐quality or low‐quality eyewitness evidence and to evaluate eyewitness factors adopting either their default or a counterfactual mindset via a question‐order manipulation. Logistic regressions and analyses of variance revealed that a counterfactual mindset lowered perceptions of eyewitness accuracy and guilty verdicts (compared with the default mindset) when the evidence was poor; a counterfactual mindset, however, did not increase perceptions of accuracy and guilty verdicts when evidence was strong. We discuss possible mechanisms underlying these effects and identify several potential avenues for future research.Copyright © 2016 John Wiley & Sons, Ltd.     

Nonadversarial Methods for Sensitizing Jurors to Eyewitness Evidence

Tested the effects, on juror decision making, of court-appointed expert testimony and judge's instructions designed to sensitize jurors to eyewitness evidence. Subjects ( N = 144) viewed a videotaped trial in which the primary evidence was the testimony of and identification by an eyewitness. Three levels of expert advice (court-appointed expert, judge's instructions, no expert advice) were crossed with two levels of witnessing and identification conditions and two levels of witness confidence The court-appointed expert produced skepticism toward the identification but did not improve juror sensitivity to the eyewitness evidence. The judge's instructions produced neither skepticism or sensitization effects.     

Habla Ingles? The Effects of Language Translation on Simulated Juror Decisions1

Two studies were conducted in which college students, acting as simulated jurors, heard the testimony of a defendant in an assault case. The testimony was presented in English or in another language (Spanish in Study 1 and Thai in Study 2) which was translated into English by an interpreter. In Study 1, non-Hispanics judged the defendant to be more guilty than did Hispanics when the defendant's testimony was presented in Spanish than when it was presented in English. This bias was offset when the judge's instructions admonished the jurors to ignore the fact that the defendant's testimony was translated. Similarly, in Study 2, subjects (all non-Thai) judged the defendent more guilty when his testimony was presented in Thai than when it was presented in English. Again, this bias was eliminated by the judge's instructions to the jurors to ignore the fact that the testimony was translated. The increased guilty verdicts for defendants who did not testify in English appeared to be due to prejudice and language ethnocentrism, the belief that defendants in U.S. courts should speak English.     

Effects of Mental Health and Neuroscience Evidence on Juror Perceptions of a Criminal Defendant: the Moderating Role of Political Orientation

Several recent studies have examined the effects of mental health and neuroscientific evidence on attitudes toward criminal defendants, suggesting that these factors may influence juror decision‐making in meaningful ways. Few studies to date have manipulated both of these variables while also considering theoretically important individual difference variables (e.g., political orientation). Using a criminal case simulation, this study manipulated the presence of evidence concerning mental disorders (psychopathy and schizophrenia) and increasing levels of neuroscientific detail regarding a defendant's brain injury, and examined verdicts and sentencing recommendations in over 400 persons attending jury duty. Main effects were detected for mental health testimony and political orientation, although interactions were noted as well. More negative reactions to defendants labeled as psychopaths were relatively consistent, whereas participants who identified as liberal generally were less punitive towards a defendant identified as schizophrenic than were more conservative jurors. Consistent with other recent research, juror perceptions of the defendant's level of psychopathic traits (independent of the effects of the experimental manipulations) predicted guilty verdicts and longer sentencing recommendations. Copyright © 2016 John Wiley & Sons, Ltd.     

Effects of inadmissible Evidence on the Decisions of Simulated Jurors: A Moral Dilemma

In a 2 × 3 design, simulated jurors received either weak or strong evidence against a defendant in a murder case. Within each evidence condition, subjects were given either additional evidence ruled admissible, additional evidence ruled inadmissible, or no additional evidence. Results indicated that ( a ) jurors were biased by inadmissible evidcnce in the weak-evidence but not in the strong-evidence condition, ( b ) strong evidence resulted in more guilty verdicts than did weak evidence, ( c ) confidence in verdict was influenced by strength of evidence, and ( d ) confidence of guilt was positively correlated with severity of punishment. Implications of the results are discussed within the context of the judicial process.     

Perceptions of Children's Credibility in Sexual Assault Cases1

Children's testimony often plays a central role in prosecutions of child sexual abuse. Nevertheless, research on jurors' perceptions of the credibility of child sexual assault victims remains limited. In three experiments, we examined mock jurors' reactions to children's testimony about sexual abuse. Participant jurors were exposed to videotaped or written scenarios of child sexual abuse trials and then rated victim credibility and defendant guilt. Analyses indicated that: (a) victim age was either inversely related or unrelated to perceptions of victim credibility, (b) women were more likely than men to find child victims credible, (c) corroborating testimony from a child victim increased the credibility of another child victim, and (d) exposure of participants to past criminal acts and other negative defendant character evidence heightened perceived victim credibility and defendant guilt. Implications for understanding jurors' reactions to child witnesses are discussed.     

Improving the Credibility of Child Sexual Assault Victims in Court: The Impact of a Sexual Assault Nurse Examiner

The present study investigated the influence of a sexual assault nurse examiner's (SANE's) testimony on mock juror perceptions of a child or adolescent victim of child sexual assault. Community members (N = 252, 156 females) read a fictional criminal trial summary of a child sexual assault case in which the victim was 6 or 15 years old and the prosecution presented medical testimony from a SANE or a traditional registered nurse (RN), or did not present medical testimony. Mock jurors were more likely to render guilty verdicts when a SANE testified compared with the other two testimony conditions. In addition, pro-victim judgments (e.g., sympathy toward the victim) and negative defendant judgments (e.g., anger toward the defendant) mediated this relation. Finally, cognitive network representations of the case demonstrated that the RN and no-medical-testimony groups were similar and the SANE group was distinct from the other two conditions. We discuss these results in terms of the implications of SANE testimony in child sexual assault court cases. Copyright © 2015 John Wiley & Sons, Ltd.     

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.     

Disjunction Between Probability and Verdict in Juror Decision Making

Although the law assumes a close relation between the probability that a defendant committed the act in question and the ensuing verdict of the jurors, prior research has shown this assumption to be often violated. We present five experiments designed to show that factors that influence probability also influence verdict, but other factors are capable of directly producing changes in verdict without affecting probability. In Experiment 1, we replicated the Wells Effect; scenarios generating the same probability that the Blue Bus Company was to blame for the same accident, nevertheless, generated significantly different likelihoods of finding the defendant liable. In Experiment 2, we showed that equally diagnostic affirmative and negative evidence had differential effects on mock jurors' probability estimates and verdicts. In Experiment 3, we showed that a completely nondiagnostic witness, who either implicates the same bus company or a different bus company as did a diagnostic witness, significantly influenced mock jurors' verdicts. However, the nondiagnostic witness did not change the probability that the Blue Bus Company was responsible for the accident. In Experiment 4, we demonstrated that base rate and witness reliability information resulted in very similar probability estimates but radically different verdicts. In Experiment 5, we showed that a change in the diagnosticity of the evidence influenced both probability and verdict with the former mediating differences in the later. Because probability is only one of the several determinants of the verdict, the two dependent variables are not as closely related as the law presumes. Copyright © 2011 John Wiley & Sons, Ltd.     

How Video Image Size Interacts with Evidence Strength,Defendant Emotion,and the Defendant–Victim Relationship to Alter Perceptions of the Defendant

Courtroom video presentations can range from images on small screens installed in the jury box to images on courtroom video monitors or projection screens. Does video image size affect jurors' perceptions of information presented during trials? To investigate this we manipulated video image size as well as defendant emotion level presented during testimony (low, moderate), the defendant–victim relationship (spouses, strangers), and the strength of the evidence (weak, strong). Participants (N = 263) read a case and trial summary, watched video of defendant testimony, and then answered a questionnaire. Larger screens generally accentuated what was presented (e.g., made stronger evidence seem stronger and weaker evidence seem weaker), acting mainly upon trial outcome variables (e.g., verdict). Non‐trial outcomes (e.g., defendant credibility) were generally affected by defendant emotion level and the defendant–victim relationship. Researchers and attorneys presenting video images need to recognize that respondents may evaluate videotaped trial evidence differently as a function of how video evidence is presented. Copyright © 2014 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.