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.     

What US judges know and believe about eyewitness testimony

In a survey, 160 US judges indicated their knowledge and beliefs about eyewitness testimony. Although correct on some issues, judges were often wrong on important issues such as whether at trial eyewitness confidence is a good indicator of eyewitness accuracy, and if jurors can distinguish accurate from inaccurate witnesses. Increased knowledge was associated with: a willingness to permit legal safeguards, including expert testimony at trial; a belief that jurors have limited knowledge of eyewitness factors; a reluctance to convict defendants solely from eyewitness testimony; a more accurate estimate of the extent to which wrongful convictions result from eyewitness error; and a belief that judges need more eyewitness training. Additional training about factors and procedures that affect eyewitness accuracy may help judges reduce the number of wrongful convictions. Copyright © 2004 John Wiley & Sons, Ltd.     

A Comparison of What U.S. Judges and Students Know and Believe About Eyewitness Testimony

We compared what 160 U.S. judges, 57 law students, and 121 undergraduates know and believe about factors affecting the accuracy of eyewitness testimony. Judges were no more knowledgeable than were undergraduates, and both groups were less knowledgeable than were law students. For all 3 groups, increased knowledge of eyewitness factors was associated with beliefs that might reduce wrongful convictions. Participants in all 3 groups underestimated what potential jurors know about eyewitness testimony. The results suggest that increasing judges' knowledge of eyewitness testimony might help them to reduce wrongful convictions and to more accurately assess when eyewitness experts are needed. The results also suggest that law schools need to do a better job of educating law students about eyewitness testimony.     

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.     

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.     

Lay knowledge of eyewitness behaviour: A British survey

One of the recent concerns in the study of eyewitness memory is how well lay knowledge, i.e. ‘common sense’, matches the findings of empirical research. A number of American and Canadian studies, some using questionnaire methodology, have found limitations in lay knowledge of eyewitness behaviour. Further studies have extended this general finding beyond the lay public–who are prospective jurors–to legal professionals such as lawyers and policemen. The present study utilized the Knowledge of Eyewitness Behaviour Questionnaire (KEBQ), an inventory used in previous studies, to replicate the North American studies with a British sample of students, including law students, and the general public. The results showed a great similarity between the North American and British samples' knowledge of eyewitness behaviour. A significant number of correct responses were made to eight of the 14 KEBQ items, with a significant number of incorrect responses to the remainder. It was also found that law students were no more knowledgeable than other subjects; that knowledge did not vary with age; and that previous experience as an eyewitness was not related to knowledge of eyewitness behaviour. In responding to some of the criticisms of questionnaire studies it is argued that the evidence is mounting in favour of the need for a recognized system to make jurors aware of the factors known to influence eyewitness testimony.     

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.     

Eyewitness memory is still not common sense: comparing jurors,judges and law enforcement to eyewitness experts

Knowledge of factors affecting eyewitness accuracy was examined in a sample of jurors, judges and law enforcement professionals. Participants completed a survey in which they were asked to agree or disagree with 30 statements about eyewitness issues, and their responses were compared to a sample of eyewitness experts who completed the same survey. Participant responses differed significantly from responses of eyewitness experts. Jurors disagreed with the experts on 87% of the issues, while judges and law enforcement disagreed with the experts on 60% of the issues. The findings show a large deficiency in knowledge of eyewitness memory amongst jurors, judges and law enforcement personnel, indicating that the legal system may benefit from expert assistance in the evaluation of eyewitness evidence. Copyright © 2005 John Wiley & Sons, Ltd.     

A Lay Perspective on the Accuracy of Eyewitness Testimony1

To understand more about what laypeople think they “know” about eyewitness testimony, 276 jury-eligible university students were asked to indicate what factors they believe affect the accuracy of eyewitness testimony. In contrast to the large proportion of eyewitness-memory research that concerns system variables, the lay respondents overwhelmingly generated factors related to estimator variables, while system-variable factors such as police questioning and identification procedures were rarely mentioned. Respondents also reported that their own common sense and everyday life experiences were their most important sources of information about the accuracy of eyewitness testimony. Not only do these results clarify the need for further research on the lay perspective of eyewitness testimony, but they also provide some insight into the way in which many jurors might approach cases involving eyewitness evidence.     

Judge's Instruction on Eyewitness Testimony: Evaluation and Revision1

Studies of the reliability of eyewitness identification show that such testimony may frequently be inaccurate; because of this inherent unreliability, the law has established certain safeguards to the use of eyewitness evidence. One safeguard has been the development of an instruction that a judge may use to focus jurors' attention on the eyewitness issue. The effectiveness of this instruction has never been assessed, although other studies confirm that jurors frequently misunderstand or incorrectly use instructions they get from the judge. The purpose of these studies was to evaluate comprehension of this instruction in the context of a videotaped trial and to develop a simplified instruction that would be easier for jurors to understand. Compared to jurors who heard the existing instruction, those with the revised version were more knowledgeable of the factors to consider when listening to eyewitness testimony and were less likely to convict the defendant. A sample of superior court judges in the U.S. thought the simplified instruction was more effective than the existing version at conveying the intended legal concepts to the jury, but also rated it as more strongly biased toward the defense.     

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 everyday production of knowledge: individual differences in epistemological understanding and juror‐reasoning skill

This study investigated the untested assumption that people's everyday reasoning reflects different understandings of the nature of knowledge and knowing. The epistemological stances of 180 prospective jurors were assessed with an interview that probed the nature and source of the discrepant knowledge claims of two historical accounts. The researchers derived global epistemological levels from these interviews. The jurors also heard trials and offered justifications for their verdict choices. The researchers assessed these justifications for whether subjects could use various reasoning skills successfully. Epistemological level, but not educational level, age, or gender, predicted juror‐reasoning skills and degree of certainty about verdict choice. Epistemological level, mediated by the juror‐reasoning skills, was a better predictor of general argument skill than certainty about verdict choice and the amount of evidence used in arguing for a verdict. The results indicate that epistemological understandings underlie specific juror‐reasoning skills and overall argument ability. Copyright © 2002 John Wiley & Sons, Ltd.     

Speech style and occupational status affect assessments of eyewitness testimony

This study examined how speech style and occupational status affect mock jurors' assessments of eyewitness testimony. Mock jurors (n = 120) watched a video of a man testifying about witnessing an attempted robbery. The eyewitness exhibited either a powerless or powerful speech style and reported either a high or low (or no) status occupation during his testimony. Results indicated that high occupation status and powerful speech style led to more favorable evaluations of the eyewitness's testimony and of the case against the defendant than powerless speech style and low/no occupation status. Implications of these results on considerations of eyewitness testimony and future research are discussed.     

Eyewitness testimony: tracing the beliefs of Swedish legal professionals

This paper examines beliefs held by Swedish legal professionals about eyewitness testimony. In a survey including questions about 13 key issues of eyewitness testimony, three groups were investigated: police officers (n = 104), prosecutors (n = 158), and judges (n = 251). The response rate was 74%. Examples of findings are that the beliefs were in line with scientific findings concerning the weapon focus effect, but were not in line for simultaneous vs. sequential lineups. Between-group differences were found for seven items. Judges were much more sceptical than police officers about the reliability and completeness of children's testimonies. The groups seldom agreed about one answer alternative, and they reported not being up to date about scientific research on eyewitness testimony. The results suggest that some important research findings have reached those working on the field. However, they hold many wrongful beliefs about eyewitness testimony, beliefs that might compromise the accuracy of legal decisions.     

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.     

An Aiibi Witness' Influence on Mock Jurors' Verdicts1

The impact of alibi testimony on juror decision making is not yet clear because it has been examined empirically infrequently. This study was designed to determine the impact of alibi witness' testimony, the impact of an alibi witness with a relationship in comparison to one without a relationship to the defendant, and the impact of an eyewitness' confidence on juror decision making. Results indicated that mock jurors acquit a defendant more often when an alibi witness with no relationship to the defendant testified on his behalf. Participants did not believe an alibi witness who had a relationship with the defendant even though the witness was not a family member. Implications for these results are discussed.     

Factors influencing juror verdict in a case involving repressed memories of abuse

Mental health professionals acting as expert witnesses are expected to testify about the prevalence of sexual abuse, and also about the veracity of memory. In cases involving adult survivors of sexual abuse, this testimony is typically about repressed and false memory syndromes. Many professionals have noted concerns about the lack of definitive data to support either syndrome. This study examined the following variables: juror knowledge and experience with repressed and false memory syndromes, juror attitudes about sexual abuse and memory recovery techniques, and gender of juror on verdict. Results include effects for repressed memory knowledge/experience and gender. Gender differences were found regarding attitudes about abuse and memory. Concluding comments include practical and research implications of the study results.     

Factors influencing juror verdict in a case involving repressed memories of abuse

Mental health professionals acting as expert witnesses are expected to testify about the prevalence of sexual abuse, and also about the veracity of memory. In cases involving adult survivors of sexual abuse, this testimony is typically about repressed and false memory syndromes. Many professionals have noted concerns about the lack of definitive data to support either syndrome. This study examined the following variables: juror knowledge and experience with repressed and false memory syndromes, juror attitudes about sexual abuse and memory recovery techniques, and gender of juror on verdict. Results include effects for repressed memory knowledge/experience and gender. Gender differences were found regarding attitudes about abuse and memory. Concluding comments include practical and research implications of the study results.