Educating Jurors about Forensic Evidence: Using an Expert Witness and Judicial Instructions to Mitigate the Impact of Invalid Forensic Science Testimony

Invalid expert witness testimony that overstated the precision and accuracy of forensic science procedures has been highlighted as a common factor in many wrongful conviction cases. This study assessed the ability of an opposing expert witness and judicial instructions to mitigate the impact of invalid forensic science testimony. Participants (N = 155) acted as mock jurors in a sexual assault trial that contained both invalid forensic testimony regarding hair comparison evidence, and countering testimony from either a defense expert witness or judicial instructions. Results showed that the defense expert witness was successful in educating jurors regarding limitations in the initial expert's conclusions, leading to a greater number of not-guilty verdicts. The judicial instructions were shown to have no impact on verdict decisions. These findings suggest that providing opposing expert witnesses may be an effective safeguard against invalid forensic testimony in criminal trials.     

Effects of Experiencing the Eyewitness Identification Procedure on Juror Decisions

Mistaken eyewitness identifications are believed to contribute to a preponderance of wrongful convictions, underscoring the need to identify methods to help decrease the likelihood of false convictions based on eyewitness testimony. The present study tested the hypothesis that providing jurors with first-hand experience with eyewitness identification procedures could help further sensitize them to the limitations of eyewitness testimony. Eighty college students watched a videotaped mock trial in which the prosecution’s sole evidence was eyewitness testimony. In a 2 × 2 randomized factorial design, we manipulated whether participants heard expert psychological testimony (henceforth referred to as expert testimony) on the limitations of eyewitness identification and whether they experienced an eyewitness identification procedure. As predicted, experiencing the eyewitness identification procedure had a significant impact on juror decisions, suggesting that this procedure could further help reduce the likelihood of wrongful convictions.     

Qualifying the psychiatrist as a lay witness: a reaction to the American Psychiatric Association petition in Barefoot v. Estelle

Organized psychiatry has recently begun to define limits to expert testimony. The American Psychiatric Association filed an amicus brief in the case of Barefoot v. Estelle urging legal curtailment of psychiatric testimony as to future dangerousness and prohibition on Constitutional grounds of expert psychiatric testimony solely based on hypothetical data. The Supreme Court refused relief on both questions. Psychiatric testimony to ultimate questions at law is limited by the inherent contextual variables of psychiatric clinical and experimental knowledge and practice. A forensic science model for psychiatric participation with explicit psychiatrically defined limitations is proposed using competence to stand trial as an example.     

Science in the Jury Box: Jurors’ Comprehension of Mitochondrial DNA Evidence

Questions about how jurors understand and apply scientific evidence were addressed in a mock jury study in which 480 jury pool members watched a videotaped mock trial that included expert testimony about mitochondrial DNA (mtDNA) evidence purportedly linking a defendant to a crime. Collectively, jurors showed moderately good comprehension of the mtDNA evidence, although some made definitional and inferential errors. Comprehension was better among jurors with higher educational attainment and more mathematics and science courses. Lower comprehension was associated with jurors’ reservations about science and concerns about the contamination of mtDNA evidence. The results suggest that most jurors are capable of comprehending and employing scientific evidence presented during trial, although errors and doubts about the evidence should be anticipated.     

测谎原理、冲突与法律思考

测谎是科学技术发展的产物，测谎证据也是自然科学与法律科学交叉共生的结果。通过鉴定结论，可以利用科学技术，给案件的侦破、公诉以及审判带来一些国家层面上的便利，但是，测谎证据同时也会引起国家利益与个人权利、科学与否的冲突。这里，问题的关键是如何给测谎证据以正确的定位。     

Considering forensic science: individual differences,opposing expert testimony and juror decision making

Two experimental studies examined the effect of opposing expert testimony on perceptions of the reliability of unvalidated forensic evidence (anthropometric facial comparison). In the first study argument skill and epistemological sophistication were included as measures of individual differences, whereas study two included scores on the Forensic Evidence Evaluation Bias Scale. In both studies participants were assigned to groups who heard: (1) no expert testimony, (2) prosecution expert testimony, or (3) prosecution and opposing expert testimony. Opposing expert testimony affected verdict choice, but this effect was mediated by perceptions of reliability of the initial forensic expert's method. There was no evidence for an effect on verdict or reliability ratings by argument skill or epistemology. In the second experiment, the same mediation effect was found, however scores on one subscale from the FEEBS and age also affected both verdict and methodological reliability. It was concluded that opposing expert testimony may inform jurors, but perceptions of the reliability of forensic evidence affect verdict, and age and bias towards forensic science influence perceptions of forensic evidence. Future research should investigate individual differences that may affect perception or bias towards forensic sciences under varying conditions of scientific reliability.     

论法医专家顾问和法医鉴定结论的质证

根据证据学的观点提出法医鉴定结论是一种科学证据,指出无论是民事诉讼还是刑事诉讼中,对其进行质证对维护司法公正的必要性和重要性。由于法医鉴定结论的专业性,对其质证时,当事或控辩双方,以及法院聘请法医专家顾问,协助对法医鉴定结论的质证具有重要的意义。     

The Impact of Negative Forensic Evidence on Mock Jurors’ Perceptions of a Trial of Drug-Facilitated Sexual Assault

Legal concerns with regard to the adverse impact of a negative toxicological screening for date-rape drugs in a case of drug-facilitated sexual assault (DFSA) were the focus of a recent Canadian case (R. v. Alouache, 2003). To assess the impact of a negative forensic report, as well as the impact of expert testimony explaining the many factors that may contribute to a negative outcome, participants (N=171) received a written trial stimulus in which the forensic evidence (negative report, negative report plus expert testimony, no negative report and no expert testimony control) and the complainant's beverage consumption (alcohol, cola) were systematically varied. Results indicate that a negative finding in the absence of expert testimony produced greater verdict leniency and more favourable evaluations of the defendant's case. In contrast, no differences were found between the case in which the expert testified and a case in which the negative report and expert testimony were omitted.

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Communicating forensic scientific expertise: An analysis of expert reports and corresponding testimony in Tasmanian courts

Forensic criminology examines the use of forensic science in society. Justice can be hampered, for example, if the communication of forensic scientific findings is unclear or misleading, even if unintentionally. Although various recommendations guide the communication of forensic science, it is unclear whether they are reflected in practice. This study explored the communication of forensic biology in 10 cases of major crimes against the person heard in the Tasmanian Supreme Court, where the standard practice is to issue brief summary reports in the first instance. The content of expert reports and corresponding testimony was analysed to determine its adherence to recommendations outlined in standards, practice notes, and research. While reports were found to be very brief, testimony elaborated on all major elements. Mostly elicited by the prosecution, some elements were volunteered by expert witnesses, or raised by defence. Overall, expert evidence in courts—but not reports (due to the use of brief summary reports)—largely adhered to recommendations. Further research is needed to determine the prevalence and effectiveness of alternative approaches to communication that were identified in certain cases.     

Expert Testimony Regarding Child Witnesses: Does It Sensitize Jurors to Forensic Interview Quality?

Does expert testimony on forensic interviews with children help adults distinguish between poorly conducted and well-conducted interviews? This study evaluates the effects of social framework expert testimony regarding child witnesses in a case involving allegations of child sexual abuse. A 2 (Expert Testimony: present or absent) × 3 (Child Forensic Interview Quality: poor, typical, or good) × 2 (Child’s Age: 4- or 10-year-old) factorial design was used to examine whether expert testimony is prejudicial or beneficial to jurors (N = 463). The results revealed that, without expert testimony, mock jurors did not consider the forensic interview quality when reaching a verdict. However, with expert testimony, mock jurors were more likely to render guilty verdicts if the interview quality was good versus poor. Further expert testimony increased mock jurors’ knowledge about child witnesses. These findings suggest that expert testimony related to the impact of interview techniques on the reliability of children’s reports may assist fact-finders in evaluating child abuse cases.     

Meeting a Forensic Podiatry Admissibility Challenge: A Daubert Case Study

This article is an introduction to the United States Supreme Court's standard of admissibility of forensic evidence and testimony at trial, known as the Daubert standard, with emphasis on how this standard applies to the field of forensic podiatry. The author, a forensic podiatrist, provided law enforcement with evidence tying a bloody sock‐clad footprint found at the scene of a homicide to the suspect. In 2014, the author testified at a pretrial hearing, known as “a Daubert hearing,” to address the admissibility of this evidence in court. This was the first instance of forensic podiatry being the primary subject of a Daubert hearing. The hearing resulted in the court ordering this evidence admissible. The expert's testimony contributed to the suspect's conviction. This article serves as a reference for forensic podiatrists and experts in similar fields that involve impression evidence, providing evidentiary standards and their impact on expert evidence and testimony.     

Peer‐Reviewed Forensic Consultation in Practice: Multidisciplinary Oversight in Common Expertise

The fallibility of forensic science consultation is an ongoing and major justice concern. Prospective peer‐reviewed forensic consultation has over 10 years of application in American criminal and civil courts, adapting from the traditional oversight of teaching hospitals, rules of evidence and discovery, conventions of testimony of expert witnesses, and attorneys' overall trial strategy. In systematizing heightened oversight, this process ensures greater accountability in forensic science consultation. The integration of peer reviewers' complementary expertise and experience enhances the sophistication and overall quality of assessment. Forensic examination frequently involves the interface of different specialties. Multidisciplinary peer review augments expert proficiency with that of professional peers having different vantage points from relevant scientific disciplines. This approach ensures greater sophistication of a case inquiry, built‐in accountability, and streamlined processes when multiple experts are necessitated. Here, the authors present examples of several cases and the primary and secondary benefits of this collaborative, rigorous, cross‐disciplinary exercise.     

Forensic Confirmation Bias: Do Jurors Discount Examiners Who Were Exposed to Task-Irrelevant Information?*†

Knowledge of task-irrelevant information influences judgments of forensic science evidence and thereby undermines their probative value (i.e., forensic confirmation bias). The current studies tested whether laypeople discount the opinion of a forensic examiner who had a priori knowledge of biasing information (i.e., a defendant's confession) that could have influenced his opinion. In three experiments, laypeople (N = 765) read and evaluated a trial summary which, for some, included testimony from a forensic examiner who was either unaware or aware of the defendant's confession, and either denied or admitted that it could have impacted his opinion. When the examiner admitted that the confession could have influenced his opinion, laypeople generally discounted his testimony, as evidenced by their verdicts and other ratings. However, when the examiner denied being vulnerable to bias, laypeople tended to believe him—and they weighted his testimony as strongly as that of the confession-unaware examiner. In short, laypeople generally failed to recognize the superiority of forensic science judgments made by context-blind examiners, and they instead trusted examiners who claimed to be impervious to bias. As such, our findings highlight the value of implementing context management procedures in forensic laboratories so as not to mislead fact-finders.     

Complex scientific testimony: How do jurors make decisions?

Critics of the civil jury system question whether jurors can adequately evaluate complex expert testimony. Based on current models of research in persuasion, we hypothesized that when expert testimony is complex, factors other than content will influence persuasion. Participants, serving as mock jurors, watched a videotaped trial in which two scientists provided evidence on whether PCBs could have caused a plaintiff's illness. The complexity of the expert's testimony and the strength of the expert's credentials were varied in a 2×2 factorial design. After watching the videotape, mock jurors rendered a verdict and completed a number of attitude measures related to the trial. Overall, consistent with our prediction, we found that jurors were more persuaded by a highly expert witness than by a less expert witness, but only when the testimony was highly complex. When the testimony was less complex, jurors relied primarily on the content of that testimony, and witness credentials had little impact on the persuasiveness of the message.     

Error Rates,Likelihood Ratios,and Jury Evaluation of Forensic Evidence

Forensic examiners regularly testify in criminal cases, informing the jurors whether crime scene evidence likely came from a source. In this study, we examine the impact of providing jurors with testimony further qualified by error rates and likelihood ratios, for expert testimony concerning two forensic disciplines: commonly used fingerprint comparison evidence and a novel technique involving voice comparison. Our method involved surveying mock jurors in Amazon Mechanical Turk (N = 897 laypeople) using written testimony and judicial instructions. Participants were more skeptical of voice analysis and generated fewer “guilty” decisions than for fingerprint analysis (B = 2.00, OR = 7.06, p = <0.000). We found that error rate information most strongly decreased “guilty” votes relative to no qualifying information for participants who heard fingerprint evidence (but not those that heard voice analysis evidence; B = −1.16, OR = 0.32, p = 0.007). We also found that error rates and conclusion types led to a greater decrease on “guilty” votes for fingerprint evidence than voice evidence (B = 1.44, OR = 4.23, p = 0.021). We conclude that these results suggest jurors adjust the weight placed on forensic evidence depending on their prior views about its reliability. Future research should develop testimony and judicial instructions that can better inform jurors of the strengths and limitations of forensic evidence.     

The Impact of Daubert on the Admissibility of Forensic Anthropology Expert Testimony

Forensic anthropologists anticipated a significant impact from the 1993 Supreme Court Daubert decision, which addressed the standard of admissibility for expert testimony. In response, many forensic articles cited Daubert in the search for objective techniques or a critique of established subjective methods. This study examines challenges to forensic anthropological expert testimony to evaluate whether Daubert has actually affected the admissibility of such testimony. Thirty cases were identified that addressed the admissibility of the testimony, including 14 cases prior to Daubert and 16 after Daubert. Examination of these cases indicates that post‐Daubert cases do not result in more exclusions. Yet, this lack of exclusions may instead be viewed as a manifestation of the field's overall surge toward more objective and quantifiable techniques in a self‐regulating response to Daubert.     

中国刑事专家辅助人向专家证人的角色转变

中国的刑事专家辅助人具有既类似于律师又类似于鉴定人、证人的多重属性;围绕专家辅助人意见的性质,也形成了质证方式说、鉴定意见说、证人证言说等多种观点。角色定位上的混乱,不仅造成了独具特色的鉴定人与专家辅助人的双轨制,而且常常使专家辅助人意见的法庭采信陷入困境。从最高人民法院有关专家辅助人的新近规定看,专家辅助人的角色呈现出向专家证人转变的趋势。这种转变的核心要求,一是实现鉴定人和专家辅助人的诉讼地位平等,专家辅助人意见和鉴定意见在专家证言意义上的证据效力平等;二是使专家辅助人回归专家证人本色,将强加给专家辅助人的不合理的质证职责交还给律师、检察官;三是提高律师、检察官熟练运用交叉询问规则、对科学证据进行质证的能力,充分发挥法官的科学证据“守门人”作用,以适应事实认定科学化的需要。     

Wrongful convictions and claims of false or misleading forensic evidence

The results are reported of a study to examine case factors associated with 732 wrongful convictions classified by the National Registry of Exonerations as being associated with “False or Misleading Forensic Evidence.” A forensic error typology has been developed to provide a structure for the categorization and coding of factors relating to misstatements in forensic science reports; errors of individualization or classification; testimony errors; issues relating to trials and officers of the court; and evidence handling and reporting issues. This study, which included the analysis of 1391 forensic examinations, demonstrates that most errors related to forensic evidence are not identification or classification errors by forensic scientists. When such errors are made, they are frequently associated with incompetent or fraudulent examiners, disciplines with an inadequate scientific foundation, or organizational deficiencies in training, management, governance, or resources. More often, forensic reports or testimony miscommunicate results, do not conform to established standards, or fail to provide appropriate limiting information. Just as importantly, actors within the broader criminal justice system—but not under the purview of any forensic science organization—may contribute to errors that may be related to the forensic evidence. System issues include reliance on presumptive tests without confirmation by a forensic laboratory, use of independent experts outside the administrative control of public laboratories, inadequate defense, and suppression or misrepresentation of forensic evidence by investigators or prosecutors. In approximately half of wrongful convictions analyzed, improved technology, testimony standards, or practice standards may have prevented a wrongful conviction at the time of trial.     

If It Walks Like a Duck: a Case of Confirmatory Bias

Confirmatory bias is an unavoidable source of error in human judgment, which is rooted in the adaptive design of the brain for recognizing meaningful patterns. In forensic psychology, the complete elimination of confirmatory bias is worth aspiring to, but even its substantial reduction is fraught with challenges. In this brief article, I present a vignette from an actual jury trial to illustrate how a seemingly small instance of confirmatory bias led to a major blunder in expert testimony. Also, I consider how it might have been prevented.