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.     

The Timing of the Defense Opening Statement: Don't Wait Until the Evidence Is in1

Defense attorneys often reserve their opening statements until after presentation of evidence by the prosecution, a practice advocated by some experts. The current study, involving 291 subjects, varied the timing of the defense attorney's opening statement so that it preceded the prosecutor's opening statement, immediately followed the prosecutor's opening statement, or was reserved until after the prosecutor's case presentation. The type of opening statement (content vs. noncontent) and the testimony (altered vs. unaltered) were varied for purposes of increasing generalization. Materials were based on an actual case of auto theft and were presented in written form complete with judge's instructions. The results showed that subjects perceived eyewitness testimony, the prosecutor's opening statement, the prosecutor's closing statement, the defense attorney's closing statement, and the effectiveness of the attorneys differently depending on the timing of the opening statement. Each of these items favored the defense more than the prosecution if the defense opening statement was earlier rather than later. These effects did not interact with type of opening statement or the testimony alteration variable. Individual verdicts, when weighted by the subjects' confidence in their verdicts, were also affected by the timing variable with verdicts more favorable to the defense when the defense opening statement was given earlier rather than later. The consistency with which the timing variable affected subjects' impressions suggests that defense attorneys who take their first opportunity to make an opening statement, rather than delay, end up with a stronger case for their client. Possible exceptions to this conclusion are discussed.     

The Determinants of Mock Jurors' Verdicts in a Rape Case1

The determinants of verdicts in a rape case were examined. Pretrial attitudes (rape empathy, juror bias, belief in a just world, and authoritarianism) were measured to ascertain both the intercorrelations among the attitudes and their predictive value of verdicts. The eye contact (staring, avoiding, or random) of the alleged rape victim with the defendant was also examined. Results showed that rape empathy was predictive of verdict. The eye contact of the alleged victim with the defendant also affected verdicts of female mock jurors. Specifically, when eye contact was avoided, more guilty verdicts were rendered. Furthermore, interpretation of eye contact was found to be a function of mock jurors' reported rape empathy. Specifically, subjects who reported empathy with the victim tended to interpret the victim's behavior as consistent with being raped. Finally, differences were found between high and low empathizers for the rape victim in what aspects of the trial were important to mock jurors' decisions.     

Gender effects on individual verdicts and on mock jury verdicts in a Simulated Acquaintance Rape Trial

Since more women than men college students vote guilty in a simulated acquaintance rape trial [e.g., G. J. Fischer (1991) “Cognitive predictors of not-guilty verdicts in a Simulated Acquaintance Rape Trial,”Psychological Reports, Vol. 68, pp. 1199–1206], guilty mock jury verdicts were expected to increase as a function of the number of women on the jury (i.e., 0, 2, 4, 6, 8, 10, and 12). However, guilty verdicts did not increase significantly until either females were an overwhelming majority (i.e., 10 women to 2 men) or the jury was all female. Even in the latter conditions, guilty verdicts were fewer than would be expected based on the 86% of women and 66% of men voting guilty on a survey completed after reading about the trial, but before serving on a jury. Although a very large majority of females were needed to increase guilty verdicts, a majority appeared to lessen the likelihood of not guilty verdicts. For example, when a majority of jurors were female, 0/18 hung juries leaned toward a not guilty verdict vs. 11/34 juries leaning toward a not guilty verdict when less than or equal to one half of the jurors were female. Most of the students were White (85%), with 4% Asian, 3.2% Black, 3.2% Hispanic, and 4% “Other.”     

Information Processing in Joined and Severed Trials

The present study was conducted to determine the process by which jurors reach verdicts in trials in which multiple charges are joined in one indictment. The experiment was designed to test the impact of joinder of affenses, similarity of offenses, and evidentiary strength of jurors' ability to process trial evidence. The results gathered from 220 male and female subjects indicated, as previous research has shown, that joined trials lead to more guilty verdicts than severed trials; that the first charge in a joined trial accounts for this "joinder effect," receiving significantly more guilty verdicts than its severed counterpart. When joined trials are composed of similar categories of crimes, guilt verdicts increase and jurors tend to confuse evidence-as shown by a high rate of antidefendant intrusions from case two to case one. More antidefendant cognitions were also found when the cases were similar. Furthermore, case similarity interacted with the evidentiary strength of the charges in joined trials.     

The Effect of Several Types of Pretrial Publicity on the Guilt Attributions of Simulated Jurors1

The experiment (N= 312) tested the effects of two types of pretrial publicity (PTP) on the guilt verdicts of simulated jurors. Heinous PTP was manipulated by varying the degree to which the lurid details of a rape-murder were presented to prospective jurors. Prejudgement PTP varied in the extent to which it implied that the defendant was the perpetrator or the rape-murder. As predicted, PTP which was high in either heinousness or prejudgment increased the females' tendency to conclude-after the trial evidence-that the defendant was guilty of the crime. The biasing effect of prejudgment PTP, however, was significant only among females categorized as being of low IQ. In contrast, neither dimension of PTF' significantly influenced the guilt verdicts of male jurors. Several possible explanations of the sex's differential vulnerability to PTP were proposed. In addition, evidence was obtained that female jurors may have been derogating the rape-murder victim and defensively minimizing the gravity of her fate, as a result of motivations to believe in a just world.     

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.     

Witnesses and Their Testimony: Effects of Ordering on Juror Verdicts1

Thibaut and Walker's claim that criminal courtroom proceedings are subject to pervasive recency effects was experimentally investigated. Previous research on order effects in a legal setting is critically reviewed; it is argued that this research fails to provide adequate simulation of courtroom protocol. An experiment was designed to retain the structure of a criminal trial while manipulating witness and testimony order. In contrast to earlier research, primacy effects were found. The greatest number of guilty verdicts by simulated jurors occurred when the strongest “guilty” witnesses and “guilty” testimony by these witnesses came first. These results are discussed with respect to (a) witness and testimony order, (b) length of case, and (c) type of case used.     

Jury Deliberations: Discussion Content and Influence Processes in Jury Decision Making1

The present research investigated the jury deliberation process. Representative juror subjects viewed a realistic videotaped trial consisting of three offenses, deliberated in groups of six and reached verdicts on each charge, and completed a post-deliberation questionnaire that assessed individual cognitions. Deliberations were videotaped and content-analyzed. The results indicated that the initial vote distribution was a good predictor of the final verdict; majorities tended to prevail. Deliberation content was concentrated primarily in two areas: (a) the facts of the case and (b) statements of preference for guilty or not guilty verdicts. Path analyses suggested that decisions on the first charge were based jointly on the content of deliberations and on the group vote distribution, whereas decisions on later charges were based largely on normative pressures. Jurors' post-deliberation impressions of the trial were affected by whether or not they had changed votes during deliberations.     

The Impact of the Guilty but Mentally III Verdict on Juror Decisions: An Empirical Analysis

The present study attempted to determine the impact of alternative verdict choices on the decisions of mock jurors. Subjects used in this study as mock jurors were all college undergraduates. They were shown one of two versions of a videotaped simulated murder trial. Both films presented a defendant who appeared to be suffering emotional difficulties, but in one film the defendant had clearly committed the act while in the other film the defendant's actions were less certain. Subjects than gave their individual verdicts and, after deliberation with other subjects, a total jury verdict. The verdicts available to the subjects varied across three conditions such that the subjects in one condition were only allowed to find the defendant to be innocent or guilty. In another condition the subjects could find the defendant innocent, guilty or not guilty by reason of insanity (NGRI). In the third condition the subjects were allowed to choose between innocent, guilty, NGRI, and guilty but mentally ill (GBMI). The results indicated that the addition of the "mental health" verdicts had a significant impact on the decisions of the jurors. In particular, it appears that only defendants who would otherwise have been found innocent were likely to be found NGRI. This study also indicated that the GBMI verdict is very attractive to mock jurors. Indeed, even innocent defendants were found to be GBMI, a form of guilt, when this alternative was made available. These findings raise potentially important constitutional and practical issues for the trial of emotionally disturbed criminal defendants.     

Juror Preference for Curative Alternative Verdicts for Veterans With PTSD

Two studies examined mock juror verdicts for veterans with PTSD in the criminal justice system. Mock jurors demonstrated a leniency toward treatment bias for veterans with PTSD who committed a violent crime, compared to a nonviolent crime. This leniency toward treatment bias occurred only when alternative verdict options, beyond guilty or not guilty, were available. In fact, a guilt bias was demonstrated by mock jurors when the only verdict options were guilty or not guilty, and a bias toward treatment was demonstrated when curative alternative verdicts were available. Implications for efforts to address the growing national problem of veterans with PTSD in the criminal justice system are discussed.     

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.     

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.     

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.     

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.     

The Effect of Capital Punishment on Jurors' Willingness to Convict

Decision-making theory suggests that jurors will tend to choose the verdict that maximizes the expected gains minus the expected losses of each decision. Capital punishment (as compared to a maximum sentence of life imprisonment) would seem to increase the perceived negative consequences of a guilty verdict without affecting the consequences of a non-guilty verdict. This should make guilty decisions less likely. To test this prediction, questionnaires were sent to all jurors who had served on 32 first degree murder trials in which capital punishment was not in effect and who reached guilty verdicts. They were asked whether their verdicts in the murder trial would have been affected if capital punishment had been a possible sentence. Thirty percent of the respondents replied that they would have been less likely to vote guilty, whereas only 3% said they would have been more likely to vote guilty. Of the 32 separate jury panels, 30 had at least one person who indicated that he or she would have been less likely to vote guilty; and in 7 trials, 50% or more of those who responded gave this answer. The results appear to indicate that the possibility of a death sentence reduces the likelihood of a guilty verdict.     

Mock Jurors’ Perception of Stalking: The Impact of Gender and Expressed Fear

Two experiments investigated mock-juror perceptions of intimate stalking using Kentucky’s (United States) anti-stalking legislation. Experiment 1 used a mock-juror methodology in which 177 undergraduates (87 men and 90 women) from a large southeastern US university read a stalking trial summary and rendered individual judgments as mock jurors. The main research question of Experiment 1 was how participant gender impacted trial judgments (e.g., verdict) when the gender of both the defendant and victim were manipulated. Overall, the results showed that men rendered significantly fewer guilty verdicts than women, particularly in conditions that included the prototypical type of intimate stalking (female victim/male defendant). In Experiment 2, also using a mock-juror methodology, 129 undergraduates (51 men and 78 women) from a large southeastern U.S. university read a stalking trial summary (involving a female victim and male defendant) and rendered individual judgments as mock jurors. The main research question of Experiment 2 focused on whether victim fear (high or low) impacted trial judgments (e.g., verdict). The results yielded an interaction of participant gender and victim fear. Specifically, whereas different levels of fear did not impact women, men yielded fewer guilty verdicts in the low victim fear condition compared to the high victim fear condition. The results of the present experiments are discussed in terms of the implications of stalking allegations brought to trial.