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.     

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.     

How expert witnesses' counterfactuals influence causal and responsibility attributions of mock jurors and expert judges

Past research has shown that counterfactual (“If…then…”) thoughts influence causal and responsibility attribution in the judicial context. However, little is known on whether and how the use of counterfactuals in communication affects lay jurors' and judges' evaluations. In two studies, we asked mock lay jurors (Study 1) and actual judges (Study 2) to read a medical malpractice case followed by an expert witness report, which included counterfactuals focused on either the physician, the patient, or external factors. Results showed that counterfactual focus had a strong effect on both lay jurors' and judges' causal and responsibility attributions. Counterfactual focus also moderated the effect of outcome foreseeability on responsibility attribution. Discussion focuses on how counterfactual communication can direct causal and responsibility attribution and reduce the importance of other factors known to influence judicial decision‐making. The potential implications of these findings in training programs and debiasing interventions are also discussed.     

Mock juror's perceptions of a child witness passing or failing a truth and lies discussion or promising to tell the truth

This study examined the effect of a child passing or failing the UK truth and lies discussion (TLD) compared with the Canadian promise to tell the truth on mock jurors' decisions regarding witness credibility and truthfulness and defendant guilt. Ninety-two participants read a vignette that described a child witnessing his father physically attacking his mother. The vignette was manipulated for witness age (age 4 years and age 8 years) and TLD performance/promise. Supporting the hypotheses, participants rated the witness's credibility and truthfulness significantly higher after a witness passed a TLD and after promising to tell the truth. The age of the child witness did not significantly affect jurors' decision making. The results are discussed in relation to arguments regarding the abolition of the UK's TLD in favour of introducing a promise to tell the truth.     

Well…ah…: Hesitations and Hedges as an Influence on Jurors' Decisions1

Hispanic jurors' verdicts and whether these decisions were related to jurors' judgments of the credibility of the witness were the focus of this experiment. A prosecution witness testified in English or in Spanish with interpretation in English. Witnesses' speaking style systematically included hedges and hesitations or did not. Guilty verdicts were independent of language of testimony. Within Spanish‐interpreted conditions, jurors convicted the defendant 47% of the time in the absence of hedges and hesitations. When he hedged and hesitated, they convicted 34% of the time. This effect was complicated by a reliable Witness Hesitation × Juror Language Dominance interaction. These results are interpreted in the context of the courtroom impact of non‐English‐speaking witnesses and the impact of interpretation.     

Effects of Testimonial Inconsistencies and Witness Group Identity on Mock‐Juror Judgments1

We examined the interaction of testimonial consistency and witness group identity on mock jurors' judgments of witness effectiveness, probability that the defendant committed the crime, and verdict. In a 3 × 2 (Witness Group Identity × Testimonial Consistency) between‐groups design, 180 mock jurors heard a trial of a person charged with assault. Although both variables affected judgments, group‐identity effects were weak when testimony was characterized by inconsistencies, and they were stronger when testimony was internally consistent but ambiguous. The judgment patterns were consistent with predictions from Chaiken, Liberman, and Eagly's (1989) heuristic‐systematic processing theory, suggesting that heuristic processing would bias systematic processing when the evidence was not decisive.     

Negative Emotions Felt During Trial: the Effect of Fear,Anger, and Sadness on Juror Decision Making

During trial, jurors may experience a variety of emotions, many of which are negative. The current study examined the effects the negative emotions anger, fear, and sadness had on jurors' sentencing decisions and explored whether the cognitive appraisal theory or the intuitive prosecutor model could explain these effects. Jurors viewed the sentencing phase of a capital murder trial and were asked to sentence the defendant. Results indicated that after viewing the trial, jurors reported increased anger and sadness, but not fear. However, only change in anger affected jurors' sentences. Jurors who reported a greater change in anger were more likely to sentence the defendant to death. This effect was mediated by the level of importance that jurors placed on the prosecution's evidence and argument. Consistent with the intuitive prosecutor model, increased anger led to higher ratings of the importance of the aggravating evidence and an increase in death sentences. Implications are discussed. Copyright © 2015 John Wiley & Sons, Ltd.     

The ‘elasticity’ of criminal evidence: a moderator of investigator bias

This study examined investigators' perceptions of the reliability of incriminating and exonerating evidence of different types. Police trainees in the role of investigators read the background of a homicide case and then received a piece of evidence that either confirmed or disconfirmed their prior suspicion against the suspect. Despite identical objective characteristics of the evidence, participants rated the disconfirming (vs. confirming) evidence as less reliable and generated more arguments to question its reliability. This asymmetrical scepticism was stronger for participants judging witness evidence, compared to DNA and photo evidence, supporting the hypothesis that different types of evidence vary in ‘elasticity’—the extent to which subjective interpretations can be justified. Interestingly, the observed effects were not limited to the specific evidence in the case, but also affected the ratings of the type of evidence in general, suggesting that reliability criteria for witness information are highly malleable and sensitive to contextual influences. Copyright © 2008 John Wiley & Sons, Ltd.     

Post‐identification feedback effects: Investigators and evaluators

We investigated the effects of post‐identification feedback and viewing conditions on beliefs and interviewing tactics of participant‐investigators, crime reports of participant‐witnesses and participant‐evaluators' credibility judgments of the witnesses. Study 1 participants assumed the roles of witness and investigator (N = 167 pairs). Witnesses' view of a simulated crime video was manipulated by distance from viewing monitor: 2 or 9 ft. Participants made a line‐up identification and received either positive feedback or no feedback. Significant effects for witnesses and investigators were associated with viewing condition and post‐identification feedback. Interviews between investigator‐witness pairs were videotaped. Investigators asked more positive, leading questions when they were led to believe that the witness had identified the suspect. In Study 2 evaluators (N = 302) viewed the witness‐investigator interviews. Viewing condition had no effect on judgments of witness credibility but positive post‐identification feedback led evaluators to judge witnesses as more credible than witnesses who received no feedback. Copyright © 2010 John Wiley & Sons, Ltd.     

The Angry Juror: Sentencing Decisions in First‐Degree Murder

A great deal of research in legal decision making has overlooked the influence of affect on the decision‐making process. The present study measured the fluctuation of emotions across five time points of a capital trial and tested the overall relationship between changes in emotion and sentencing decisions. The results showed that across all participants, anger initially increased and then decreased during the course of a capital punishment trial. Most importantly, the more individual mock jurors' anger increased during any stage of the trial, the more likely they were to assign a death sentence. Furthermore, when jurors' anger increased, they rated mitigating factors presented by the defense as weaker and the weaker mitigation mediated the relationship between change in anger and sentencing. The paper ends with a discussion of theoretical explanations and policy implications. Copyright © 2012 John Wiley & Sons, Ltd.     

Perception of line‐up suggestiveness: effects of identification outcome knowledge

Research on the hindsight bias has shown that knowledge of an event outcome makes the observed outcome appear more predictable than it does in the absence of outcome knowledge. It was hypothesised that perceptions of the suggestiveness of a line‐up would be similarly influenced by knowledge of a witness' identification decision, with a positive identification of the suspect increasing, and a negative non‐identification decreasing, perceived suggestiveness. The ratings of undergraduate students (N = 50) in Experiment 1 showed the predicted influence of positive outcome, whereas negative outcome had no demonstrable influence. In contrast, Experiment 2, conducted with police trainees (N = 126) and with the line‐up presented in the context of a criminal investigation, partially supported the predicted influence of negative, but not positive, outcome. The discrepant findings are discussed in terms of the cognitive mechanisms underlying the hindsight bias and the implications for real‐life judgements of line‐up suggestiveness. Copyright © 2010 John Wiley & Sons, Ltd.     

The influence of lawyers' questions on witness accuracy,confidence, and reaction times and on mock jurors' interpretation of witness accuracy

Two studies demonstrate the influence of lawyers' complex questions on mock‐witness accuracy, confidence, and reaction times and on the interpretation of witness accuracy by mock jurors. In study one, 32 mock witnesses were shown a short film and then questioned either with lawyers' complex questions or simple alternatives. In Study 2, 20 mock jurors viewed video footage of the mock witnesses assigned to each of the two previous conditions and were asked to rate their confidence in the witnesses' answers. The findings of the two studies indicated that lawyers' use of confusing questions reduce not only accuracy but also speed of response and both witnesses' and jurors' ability to determine accuracy. The implication of these findings is straightforward, lawyers should ask simple questions wherever possible. Copyright © 2010 John Wiley & Sons, Ltd.     

Child‐Witness and Defendant Credibility: Child Evidence Presentation Mode and Judicial Instructions1

Child‐witness presentation mode, judicial instructions, and deliberation stage effects on juror ratings of child witness and defendant were investigated Perceptions of the impact of presentation mode on witnesses, juror task, and justice also were explored. Participants (N= 108) viewed a simulated child sexual abuse trial videotape. Overall child‐witness credibility was significantly more positive with videodeposition or court‐given child evidence than with videolink. The defendant was seen as more definitely guilty when child testimony was court given than by videodeposition or videolink. Presentation mode also significantly influenced perceived impact on child witness, defendant case, and juror task. Judicial instructions interacted with presentation mode to affect perceptions of impact on child witness and juror task. Findings are discussed in relation to previous research, and implications for future research and practice are outlined.     

Effects of Considering Who and Why the Defendant Attacked1

Some people who are accused of a crime admit to the act, but provide an excuse. The effects of an excuse's self‐inflictedness level (high, moderate, or low) and the type of victim attacked (one partially responsible for the defendant's excusing condition, or innocent victim) were investigated. After a pretest (N= 26) to choose stimuli, participants (N= 220) read a scenario in which a male attacks another and then, once on trial, gives an excuse for his act. Those giving highly vs. less self‐inflicted excuses were more likely to receive a guilty verdict, received higher guilt level ratings, and tended to receive longer sentences; those who hurt an innocent vs. a partially responsible victim were more likely to be found guilty. In addition, the defendant's sentence was influenced by both the type of victim and the self‐inflictedness level of the excuse. The influence of perceived responsibility for an act on jurors' decisions is discussed     

The elimination‐plus lineup: Testing a modified lineup procedure with confidence

The present study examined whether a modified form of a preidentification confidence rating would provide evidence of a suspect's guilt in addition to the identification decision confidence. Participants (N  = 241) viewed a videotaped mock crime and were presented with a target‐present or target‐absent simultaneous, sequential, elimination, or elimination‐plus lineup procedure; both elimination procedures required 2 separate judgments from the witness (i.e., relative and absolute). The elimination‐plus procedure was identical to that of the elimination procedure with the addition of the confidence rating in between judgment 1 and judgment 2. Confidence after judgment 1, confidence after judgment 2, and the average of the 2 confidence ratings with the elimination‐plus procedure significantly predicted accuracy for choosers. Given that confidence has been recognised by the Supreme Court of the United States, these results shed light on a novel way of utilising confidence in the investigative process.     

Witness Vetting: What Determines Detectives' Perceptions of Witness Credibility?

During the course of a criminal investigation witness vetting, a detective's process of determining the credibility and weight of witness information, can lead to errors in an investigation that can go virtually unchallenged. Witness confidence, opportunity to view, and type of information proffered were examined in relation to detective inferences about witness reliability, accuracy, and probable cause to arrest. Experiment 1 involved 39 sworn law enforcement officers, and experiment 2 involved 43 sworn law enforcement officers and 86 mock detectives. Participants viewed a digital recording depicting a witness describing a gas station robbery (Experiment 1) or a campus mugging (Experiment 2). Witness confidence and detectives' inferences about culprit information influenced the vetting process and lent credibility to a confident witness whose accuracy was objectively unknown. Furthermore, the evidence indicates that sworn law enforcement are comparable with untrained observers in their use of social inference cues (i.e. confidence) in determining witness credibility; however, social inference can be assuaged by the rational, rule‐governed, decision framework established for witness vetting. Social inference processes inherent in the detective‐witness dyad is influenced by legal procedures in vetting witness information. Copyright © 2013 John Wiley & Sons, Ltd.