Criminology Communicating Scientific Findings in the Courtroom
by
Joëlle Vuille, Nicole M. Egli Anthonioz
  • LAST REVIEWED: 19 October 2018
  • LAST MODIFIED: 26 May 2016
  • DOI: 10.1093/obo/9780195396607-0198

Introduction

The number of civil and criminal trials in which there is presented at least one piece of scientific evidence—by which we mean the analysis and interpretation of physical evidence derived from the so-called hard sciences (thus excluding the fields of psychology, psychiatry, and the social and behavioral sciences)—is constantly increasing. Yet the fact finders, be they judges or juries or the attorneys arguing the cases, have limited scientific education. In this context, the way scientific experts express the results of analyses and interpretations carried out, as well as the way the members of the court understand the content of their message, is of utmost importance. Misunderstandings do happen and have dramatic consequences, as an abundant literature on wrongful convictions now well illustrates. It is thus urgent that forensic scientists learn to write more transparent statements. This requirement is also set out in a landmark report published in 2009 by the National Research Council. Following this trend, the forensic community has started developing guidelines concerning statement writing, and a structured approach to communication of expert opinion in court is now emerging. However, empirical results as to what constitutes good practice in the expression of results, and particularly the uncertainty attached to scientific results, are not abundant. Indeed, while guidelines exist, the improvement in mutual understanding is not evident. This quest for mutual understanding, in particular in the expression of evidential value, is the subject of the following bibliography.

General Issues in Communicating about Science

This section first presents publications that situate the problem of communicating scientific facts and interpretations to fact finders and making decisions based on such evidence. The journals offer the same general overview: the (mis)understanding of science by the public, as well as the more specific topic of integrating scientific evidence in the judicial decision-making process.

Articles and Books

The first source, Kahnemann, et al. 1982, situates the problem of decision making under uncertainty, which is the core issue in the field of communicating scientific findings in the courtroom. Fischhoff 2013 gives an excellent introduction to science communication on various subjects, while Redmayne 2001 and Faigman 2000 bring together the subjects of communication, uncertainty, and decision making in the legal context. A recommended starting point for the general issue of science communication is Dunwoody 2011.

  • Dunwoody, Sharon. 2011. Science communication. In Oxford Bibliographies. Edited by Patricia Moy.

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    The generalities of science communication, its history, and in particular the communication of science through mass media, are central items of this bibliography, which represents an excellent starting point on the subject.

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    • Faigman, David L. 2000. Legal alchemy: The use and misuse of science in the law. New York: Macmillan.

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      Written by a major scholar in the field, this book explores how scientific information is used in the courtroom. It is a fascinating illustration of many issues permeating the field.

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      • Fischhoff, Baruch. 2013. The sciences of science communication. Proceedings of the National Academy of Sciences of the United States of America 110.Suppl 3: 14033–14039.

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        A complete overview of how science communication informs decision making in general. This overview is illustrated by examples from different subjects.

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        • Kahnemann, Daniel, Paul Slovic, and Amos Tversky, eds. 1982. Judgment under uncertainty: Heuristics and biases. Cambridge, UK: Cambridge Univ. Press.

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          Although this book is not about communication, it highlights the way humans treat uncertainty in order to make decisions. Given that this treatment is often not rational but influenced easily by biases, these should be taken into account in communication of uncertainty.

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          • Redmayne, Mike. 2001. Expert evidence and criminal justice. Oxford: Oxford Univ. Press.

            DOI: 10.1093/acprof:oso/9780198267805.001.0001Save Citation »Export Citation »E-mail Citation »

            An inventory of the important topics pertaining to communicating scientific facts in the judicial process, illustrated by case law, and including a critique of laboratory studies.

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            Journals

            Three journals in particular cover the issue of science communication, and two of them offer a general approach (Public Understanding of Science, Science Communication), while the third is centered on human behavior in the legal context and processes (Law and Human Behavior).

            • Law and Human Behavior.

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              A multidisciplinary journal, also covering the communication of scientific knowledge in the context of the law. Although not central, issues related to decision making are also covered, making it an essential reference in the context of decision making under uncertainty, communication of scientific elements, and the law. Available online by subscription.

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              • Public Understanding of Science.

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                International journal, established in 1992, treating subjects related to the perception and role of science in society. As the name indicates, the journal centers on the general public’s relationship with science, addressing subjects such as science education, science perception, and attitudes toward science. Available online by subscription.

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                • Science Communication.

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                  Called Knowledge: Creation, Diffusion, Utilization until 1994, this journal addresses science communication issues both among professionals and between professionals and the public. It covers issues related to the content of communications, such as risk and uncertainty, and includes many articles on how to communicate in a given context. Available online by subscription.

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                  Current Practices of Statement Formulation

                  Current practices are often determined by domain-specific professional bodies issuing guidance as to the proper formulation of statements in the fields of forensic DNA analysis, document examination, fingerprint comparisons, tool marks, etc. This leads to different rules being issued in different disciplines. With the exception perhaps of the field of forensic DNA analysis (Budowle, et al. 2000), these statements often address the hypothesis of identity of source, using such wording as individualization (or same source), exclusion (or different source), and inconclusive, where this last category may be populated with authorized expressions such as “the mark was probably made by the suspect.” The first such guideline stems from SWGFAST, which only allows the use of the three most basic statements. The International Association for Identification theoretically allows its practitioners to make probabilistic statements for friction ridge comparisons but only in certain circumstances. The conclusion scale for shoeprint and tool-mark examiners (European Network of Forensic Science Institutes 2006) incites scientists to formulate conclusions concerning the probability of the cause of the mark. This is in contradiction with the recommendations presented in the section Guidelines Developed by Forensic Science Communities that preconize the evidence be evaluated in the light of competing propositions. The approaches promulgated by professional bodies and presented here are criticized in a landmark report from the National Research Council 2009, and the systematic over-claiming resulting from categorical statements is explained and criticized by Cole 2007.

                  Guidelines Developed by Forensic Science Communities

                  Researchers have addressed the question of statements offered by forensic practitioners and, in particular, the problem of over-statement in forensic science. Cook, et al. 1998 discusses the formulation of statements as a prolongation of the general approach to the evaluation of evidence. Association of Forensic Science Providers 2009 and ENFSI 2015 (the second document being explicitly based on the first) draw on this approach and provide precise instructions for forensic scientists, as well as many examples. The use of qualitative statements and verbal scales has also been proposed recently (see a full discussion in Nordgaard, et al. 2011). However, these verbal scales also draw criticism; Mullen, et al. 2014 shows that the interpretation of a given term of the scale by laypeople greatly varies. Furthermore, it shows that low values of the scale are weighted higher with respect to the intended meaning (i.e., too much weight is attributed) and that the converse is true for high values of the scale.

                  • Association of Forensic Science Providers. 2009. Standards for the formulation of evaluative forensic science expert opinion. Science and Justice 49:161–164.

                    DOI: 10.1016/j.scijus.2009.07.004Save Citation »Export Citation »E-mail Citation »

                    Issued by the forensic science providers of the United Kingdom, this standard mainly stipulates the use of likelihood ratios in evaluative opinions. It also introduces a verbal scale for qualitative expression of these opinions.

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                    • Cook, Roger, Ian W. Evett, Graham Jackson, Phil J. Jones, and Jim A. Lambert. 1998. A hierarchy of propositions: Deciding which level to address in casework. Science and Justice 38:231–239.

                      DOI: 10.1016/S1355-0306(98)72117-3Save Citation »Export Citation »E-mail Citation »

                      Explains how the hierarchical levels of propositions and evaluation of evidence will yield statements that are fit for purpose. Such statements must always address the highest level of propositions possible, given the available information.

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                      • ENFSI. 2015. ENFSI Guideline for evaluative reporting in forensic science. European Network of Forensic Science Institutes.

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                        A formalization of the use of likelihood ratios in evaluative reports, aiming at a standardized approach between different evidence types as well as across borders. The use of likelihood ratios is explained and richly illustrated with examples from various forensic fields.

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                        • Mullen, Carrie, Danielle Spence, Linda Moxey, and Allan Jamieson. 2014. Perception problems of the verbal scale. Science and Justice 54:154–158.

                          DOI: 10.1016/j.scijus.2013.10.004Save Citation »Export Citation »E-mail Citation »

                          Researchers showing that verbal scales, conceived to facilitate communication between scientists and the courts, do not fulfill this task. Indeed, qualitative designations seem to systematically be understood differently than how they were meant.

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                          • Nordgaard, Anders, Ricky Ansell, Weine Drotz, and Lars Jaeger. 2011. Scale of conclusions for the value of evidence. Law, Probability and Risk 11:1–24.

                            DOI: 10.1093/lpr/mgr020Save Citation »Export Citation »E-mail Citation »

                            A complete article on the development of a verbal scale used operationally.

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                            Rules Set Out by Courts Confronted with Scientific Evidence

                            In common law jurisdictions, scientific evidence must first be admitted by the court before they can be presented to a jury (see Oxford Bibliographies article Forensic Science). Once scientific evidence is admitted, courts of law sometimes opine as to how scientific experts should express the results drawn from scientific analyses and interpretations. Five major court cases are presented here: R. v. Adams and R. v. Doheny and Adams, which are two older decisions from England and Wales, Llera Plaza I and II, two decisions from the United States rendered in the same case of fingerprinting and the more recent R. v. T from the England and Wales Court of Appeal. These decisions all sparked heated debates in the legal and forensic science communities when they were released. Jurisdictions in Continental Europe, on the other hand, seem not to have rendered any major decision on this topic.

                            • R. v. Adams. 2 Cr App R 467, Crim LR 898, 1996.

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                              In this case pertaining to DNA evidence, the Court of Appeal excluded explicit Bayesian reasoning for use in jury trials. It famously held: “To introduce Bayes’ Theorem, or any similar method, into a criminal trial plunges the jury into inappropriate and unnecessary realms of theory and complexity deflecting them from their proper task.” This sentence was later mocked by many scholars.

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                              • R. v. Doheny and Adams. 1 Crim App R 369, 1996.

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                                According to this decision, expert witnesses must express the probative value of DNA evidence with “random occurrence ratios” (as the court called them), but they should not opine as to the probability that the defendant left the crime scene stain.

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                                • R. v. T. All ER (D) 240 (2010).

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                                  In this case (pertaining to footwear evidence), the Court of Appeal of England and Wales held that forensic results should not be expressed in the form of a likelihood ratio outside the field of DNA evidence, as long as there is no hard statistical data to back up the expert witness’s claims. This judgment has widely been criticized in the legal and scientific communities as misguided.

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                                  • US v. Llera Plaza I. 179 F. Supp.2d 492 (E.D. Pa. 2002).

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                                    In Llera-Plaza I, a federal judge held that forensic examiners could not conclude that a latent print originated from a particular individual: this is because the reliability of fingerprint comparisons had yet to be scientifically demonstrated.

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                                    • US v. Llera Plaza II. 188 F. Supp.2d 549 (E.D. Pa. 2002).

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                                      After being urged to reconsider, the judge in Llera-Plaza reversed himself. These two decisions are milestones in the debate over the way in which experts can express their conclusions in the field of fingerprinting.

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                                      Errors Made by Laypeople When Assessing Probabilities

                                      Starting with the seminal article Thompson and Schumann 1987, researchers in the field of forensic science have been investigating the errors made by non-scientists in the use of probabilities. Over the years, they have shown that decision makers are prone to all sorts of fallacious thinking when dealing with probabilities, which can lead them to render verdicts that are not logically supported by the evidence presented to them. Nance and Morris 2002 documents various mistakes made by subjects when confronted with probabilistic data. Similarly, and talking about low probabilities, Koehler and Macchi 2004 shows that mock jurors are influenced by the availability of exemplar; if a random match probability is presented as 2 in 2,000, it is less persuasive concerning the guilt of the putative source than when it is presented as 0.1 in 100. De Keijser and Elffers 2010 shows that a large proportion of judges, lawyers, and experts fail to identify the prosecutor’s fallacy as an erroneous interpretation of evidence, while Martire, et al. 2013 shows that a majority of respondents invert weak evidence when it is communicated on a verbal scale: that is to say, they interpret weakly inculpating evidence as indicating innocence. Vuille 2011 investigated how the Swiss judiciary handles DNA evidence and found that interpretational errors are quite common even among professional judges. Developed principally after the advent of forensic DNA analysis, a technique whose results have traditionally been presented in a probability format, this literature has gained importance lately as more scientists and lawyers advocate the use of explicit probabilities in all fields of the forensic sciences.

                                      • de Keijser, Jan, and Henk Elffers. 2010. Understanding of forensic expert reports by judges, defense lawyers and forensic professionals. Psychology, Crime and Law 18.2: 191–207.

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                                        Shows that Dutch defense lawyers and criminal judges have a poor understanding of the exact meaning of likelihood ratios. Their performance does not seem to be correlated with formal education, exposition to likelihood ratios in the past, or self-confidence. Comparatively, Dutch forensic scientists had a better understanding of likelihood ratios yet still made mistakes.

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                                        • Koehler, Jonathan J., and Laura Macchi. 2004. Thinking about low-probability events: An exemplar-cuing theory. Psychological Science 15.8: 540–546.

                                          DOI: 10.1111/j.0956-7976.2004.00716.xSave Citation »Export Citation »E-mail Citation »

                                          This study suggests that jurors attach more weight to the defendant’s claim that the DNA match incriminating him is coincidental when it is easy for them to imagine instances in which a random individual could have matched the crime scene material. Based on exemplar-cueing theory, the study found that the way a DNA match is expressed impacts the perceived strength of the evidence, the assessed probabilities of source and guilt, and the verdicts.

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                                          • Martire, Kristy A., Richard I. Kemp, Ian Watkins, Malindi A. Sayle, and Ben R. Newell. 2013. The expression and interpretation of uncertain forensic science evidence: Verbal equivalence, evidence strength, and the weak evidence effect. Law and Human Behavior 37.3: 197.

                                            DOI: 10.1037/lhb0000027Save Citation »Export Citation »E-mail Citation »

                                            Fascinating study suggesting the existence of a “weak evidence effect” in a case of footwear comparison: when confronted with verbal evidence weakly supporting the prosecution hypothesis, the majority of participants interpreted it as supporting the defense hypothesis.

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                                            • Nance, Dale A., and Scott B. Morris. 2002. An empirical assessment of presentation formats for trace evidence with a relatively large and quantifiable random match probability. Jurimetrics 403–448.

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                                              Among other things, this study documents all sorts of errors made by jurors when assessing the weight of statistical evidence. Besides the well-known prosecutor’s and defense attorney’s fallacies, the authors also identify a bizarre mistake that they coined “the inversion fallacy” (and that they do not use synonymously with “prosecutor’s fallacy” the way others do) in which participants equated the random match probability with the probability of guilt.

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                                              • Thompson, William C., and Edward L. Schumann. 1987. Interpretation of statistical evidence in criminal trials: The prosecutor’s fallacy and the defense attorney’s fallacy. Law and Human Behavior 11.3: 167.

                                                DOI: 10.1007/BF01044641Save Citation »Export Citation »E-mail Citation »

                                                Pioneering study showing how the evidence presentation format favors certain errors in statistical reasoning. A must read.

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                                                • Vuille, Joëlle. 2011. Ce que la justice fait dire à l’ADN (et que l’ADN ne dit pas vraiment), Étude qualitative de l’évaluation de la preuve par ADN dans le système judiciaire pénal suisse. PhD diss., Lausanne UNIL.

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                                                  Based on qualitative interviews and case studies, this study conducted in Switzerland illustrates the limited understanding that criminal justice professionals practicing in an inquisitorial jurisdiction have of forensic DNA evidence and probability statements.

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                                                  Jurors’ Understanding of Scientific Findings

                                                  Jurors have long been a source of worry for scholars interested in the use of scientific evidence in the courtroom. Deemed to be easily impressed by the (apparent) infallibility of science and by the credentials of scientific expert witnesses, jurors have always been considered a hazard to judicial fact finding when scientific evidence is presented. One of the first lines of research has thus been to compare jurors’ and judges’ performances when assessing scientific evidence (see, for example, Hans 2007), often finding little difference between the two groups. Other researchers have investigated specific issues pertaining to how jurors understand scientific evidence presented to them: for instance, the understanding of probabilities in Kaye and Koehler 1991 and the ability to detect threats to the validity of the evidence in McAuliff, et al. 2009. Another major research program has been to compare jurors’ performances to a Bayesian norm; see, for instance, Smith, et al. 1996. Thompson and Newman 2015 also compares jurors’ assessments to such a norm, varying presentation formats and evidence types. Finally, Cole and Dioso-Villa 2007 offers a review of the so-called CSI effect, according to which juries acquit suspects when the evidence presented in the courtroom does not reach the standards set out in certain TV shows.

                                                  • Cole, Simon A., and Rachel Dioso-Villa. 2007. CSI and its effects: Media, juries, and the burden of proof. New England Law Review 41.3: 435–469.

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                                                    Discusses whether media communications around scientific evidence perverts the criminal justice processes by modifying the standard and burden of proof. A fascinating read and an excellent introduction to the topic.

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                                                    • Hans, Valerie P. 2007. Judges, juries, and scientific evidence. Journal of Law and Policy 16:19–46.

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                                                      Compares judges’ and jurors’ reactions to mitochondrial DNA evidence and finds them fundamentally similar (a conclusion often reached in the literature comparing these two groups).

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                                                      • Kaye, David H., and Jonathan J. Koehler. 1991. Can jurors understand probabilistic evidence? Journal of the Royal Statistical Society, Series A 154.1: 75–81.

                                                        DOI: 10.2307/2982696Save Citation »Export Citation »E-mail Citation »

                                                        Two major scholars in the field reviewing the literature suggesting that jurors undervalue scientific evidence (compared to a Bayesian norm) when other evidence is available. A finding many times confirmed, even if some studies reach opposite conclusions.

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                                                        • McAuliff, Bradley D., Margaret B. Kovera, and Gabriel Nunez. 2009. Can jurors recognize missing control groups, confounds, and experimenter bias in psychological science? Law and Human Behavior 33.3: 247.

                                                          DOI: 10.1007/s10979-008-9133-0Save Citation »Export Citation »E-mail Citation »

                                                          Jurors do not consistently detect threats to the internal validity of psychological science studies presented during a trial. In this instance, participants detected correctly that a missing control group would affect the meaning of the results; however, they did not detect the threats posed to the validity of the study by a confounding factor and experimenter bias.

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                                                          • Smith, Brian C., Steven D. Penrod, Amy L. Otto, and Roger C. Park. 1996. Jurors’ use of probabilistic evidence. Law and Human Behavior 20.1: 49.

                                                            DOI: 10.1007/BF01499132Save Citation »Export Citation »E-mail Citation »

                                                            Manipulated the strength of seven pieces of scientific and non-scientific evidence, as well as the presence or absence of logical fallacies. Also studied these fallacies’ impact on jurors’ estimations of guilt. Good overall performance of jurors compared to a Bayesian norm, even if there was much variation among jurors.

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                                                            • Thompson, William C., and Eryn J. Newman. 2015. Lay understanding of forensic statistics: Evaluation of random match probabilities, likelihood ratios and verbal equivalents. Law and Human Behavior 39.4: 332.

                                                              DOI: 10.1037/lhb0000134Save Citation »Export Citation »E-mail Citation »

                                                              Using three different presentation formats for two different types of forensic evidence (DNA and shoeprints), the authors show that mock jurors assess the weight of DNA evidence in agreement with Bayesian norms but not the weight of shoeprint evidence. The presentation format also plays a role, in that likelihood ratios and verbal equivalents allow a correct assessment of DNA evidence but not of shoeprint evidence.

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                                                              Impact of the Form of Presentation of Scientific Findings on Laypeople

                                                              Psychological research suggests that facts that are scientifically equivalent are sometimes treated differently by decision makers simply because the way they are presented varies. This line of research is relevant in the field of scientific evidence, since the same evidence can be presented in a number of ways, depending on formal and informal rules in a given scientific community and individual preferences of the analyst. After a good general introduction in Hoffrage, et al. 2000, researchers should be directed to the work of the leading scholar in the field: Koehler 2001 and Koehler 2011. Nance and Morris 2005 explores the topic of probabilistic format further, while McQuiston-Surrett and Saks 2009 compares the relative impacts of numbers and qualitative statements. Finally Bornstein 2004 suggests that a good story always has more impact than abstract data.

                                                              • Bornstein, Brian H. 2004. The impact of different types of expert scientific testimony on mock jurors’ liability verdicts. Psychology, Crime and Law 10.4: 429–446.

                                                                DOI: 10.1080/1068316030001629292Save Citation »Export Citation »E-mail Citation »

                                                                Suggests a plaintiff is more likely to win his or her case when a scientific expert presents anecdotal case histories in support of the plaintiff’s case rather than abstract empirical data.

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                                                                • Hoffrage, Ulrich, Samuel Lindsey, Ralph Hertwig, and Gerd Gigerenzer. 2000. Communicating statistical information. Science 290.5500: 2261–2262.

                                                                  DOI: 10.1126/science.290.5500.2261Save Citation »Export Citation »E-mail Citation »

                                                                  A succinct review of the literature on how presentation format impacts people’s understanding of statistical data. Concludes that statistics expressed as frequencies (as opposed to probabilities) improve statistical thinking.

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                                                                  • Koehler, Jonathan J. 2001. When are people persuaded by DNA match statistics? Law and Human Behavior 25.5: 493.

                                                                    DOI: 10.1023/A:1012892815916Save Citation »Export Citation »E-mail Citation »

                                                                    Study carried out by one of the most prolific scholars in the field. Suggests that single-target formats lead to higher-assessed probabilities of guilt than multitarget formats and that probability formats lead to higher-assessed probabilities of guilt than frequency formats.

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                                                                    • Koehler, Jonathan J. 2011. If the shoe fits they might acquit: The value of forensic science testimony. Journal of Empirical Legal Studies 8.s1: 21–48.

                                                                      DOI: 10.1111/j.1740-1461.2011.01225.xSave Citation »Export Citation »E-mail Citation »

                                                                      In this study, jury-eligible participants were more persuaded by forensic results that did not contain any mention of a threat to the validity of the evidence than by evidence that was objectively stronger because it took those risks into account. An important study at a time when scholars demand increased transparency from experts.

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                                                                      • McQuiston-Surrett, Dawn, and Michael J. Saks. 2009. The testimony of forensic identification science: What expert witnesses say and what fact-finders hear. Law and Human Behavior 33.5: 436.

                                                                        DOI: 10.1007/s10979-008-9169-1Save Citation »Export Citation »E-mail Citation »

                                                                        In this study, McQuiston-Surrett and Saks varied the format of presentation of scientific evidence given to participating judges and jurors. The results suggest that both jurors and judges are more persuaded by qualitative conclusions (“it matches” or “the hair is similar in all microscopic characteristics”), and objective single-probability forms of testimony, than by subjective probabilities and objective multifrequency forms.

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                                                                        • Nance, Dale A., and Scott B. Morris. 2005. Juror understanding of DNA evidence: An empirical assessment of presentation formats for trace evidence with a relatively small random‐match probability. Journal of Legal Studies 34.2: 395–444.

                                                                          DOI: 10.1086/428020Save Citation »Export Citation »E-mail Citation »

                                                                          Comparing the impact of various presentation formats of scientific evidence (match, frequencies, likelihood ratio, chart), this study suggests that a) the presentation format affects the assessed probability of guilt and that b) jurors tend to undervalue the strength of scientific evidence when compared to a Bayesian norm, regardless of presentation format.

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                                                                          Extraneous Factors Influencing the Evaluation of Scientific Findings by Fact Finders

                                                                          Communicating scientific results in court is complex not only because of the substance of the message to be communicated but also because fact finders tend to be influenced by the messenger and sometimes even by the context in which the communication occurs. This phenomenon is a heuristic way of reasoning and has been the subject of fascinating studies in the realm of judicial decision making. Cooper, et al. 1996 and Ivković and Hans 2003 suggest that jurors are more swayed by the messenger than the message, especially when the content of the testimony is complex. A body of psychological research represented here by McKimmie, et al. 2004 as well as Neal and Brodsky 2008 also suggests that fact finders are influenced by extraneous factors when assessing the probative value of scientific evidence, even when they are not directly relevant. Shuman, et al. 1996 explores a number of variables, while Smith, et al. 2011 investigates more precisely the impact of case context. Finally, Cooper and Hall 2000 contributes to the decades-long debate over the virtues of court-appointed experts.

                                                                          • Cooper, Joel, and Joan Hall. 2000. Reaction of mock jurors to testimony of a court appointed expert. Behavioral Sciences and the Law 18.6: 719–729.

                                                                            DOI: 10.1002/bsl.414Save Citation »Export Citation »E-mail Citation »

                                                                            Compares the impact of testimony by expert witnesses hired by the parties versus by the court on mock jurors. Mock jurors favored the court-appointed expert whether he sided with the plaintiff or the defendant, except when the defendant was a corporation rather than an individual.

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                                                                            • Cooper, Joel, Elizabeth A. Bennett, and Holly L. Sukel. 1996. Complex scientific testimony: How do jurors make decisions? Law and Human Behavior 20.4: 379.

                                                                              DOI: 10.1007/BF01498976Save Citation »Export Citation »E-mail Citation »

                                                                              Having listened to the testimony of two scientists, mock jurors were more persuaded by the expert with the higher credentials—but only when the content of the testimony was complex. When the testimony was less complex, the credentials of the testifying expert had little impact.

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                                                                              • Ivković, Sanja K., and Valerie P. Hans. 2003. Jurors’ evaluations of expert testimony: Judging the messenger and the message. Law and Social Inquiry 28.2: 441–482.

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                                                                                Based on in-depth qualitative analysis, this study suggests that when confronted with complex expert testimony, jurors consider both the messenger and the message when evaluating an expert’s credibility. Among the factors influencing jurors’ reaction to a testimony are general impressions, credentials of the experts, motives of the experts, and presentation style and content of the testimony.

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                                                                                • McKimmie, Blake M., Cameron J. Newton, Deborah J. Terry, and Regina A. Schuller. 2004. Jurors’ responses to expert witness testimony: the effects of gender stereotypes. Group Processes and Intergroup Relations 7.2: 131–143.

                                                                                  DOI: 10.1177/1368430204043724Save Citation »Export Citation »E-mail Citation »

                                                                                  The authors find that the impact of the expert is greater when the gender of the expert is stereotypically congruent with the case’s domain (price fixing in automobile service versus cosmetics sales) than when it is incongruent. This effect seems to be mediated through the credibility accorded to the expert.

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                                                                                  • Neal, Tess M., and Stanley L. Brodsky. 2008. Expert witness credibility as a function of eye contact behavior and gender. Criminal Justice and Behavior 35.12: 1515–1526.

                                                                                    DOI: 10.1177/0093854808325405Save Citation »Export Citation »E-mail Citation »

                                                                                    This study suggests that experts who maintain a high level of eye contact with mock jurors are rated significantly more credible than experts with medium or low levels of eye contact. This only seems to apply to male expert witnesses, no such effects having been found for female expert witnesses.

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                                                                                    • Shuman, Daniel W., Anthony Champagne, and Elizabeth Whitaker. 1996. Assessing the believability of expert witnesses: Science in the jury box. Jurimetrics 37:23.

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                                                                                      Based on the survey of former civil case juries, this study suggests that believability of expert witnesses depends on perceived qualifications of the expert, familiarity with the facts, good reasoning, and impartiality. It also seems to vary according to the side calling the expert but not with the occupation of the expert or his or her appearance and personality.

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                                                                                      • Smith, Lisa L., Ray Bull, and Robyn Holliday. 2011. Understanding juror perceptions of forensic evidence: Investigating the impact of case context on perceptions of forensic evidence strength. Journal of Forensic Sciences 56.2: 409–414.

                                                                                        DOI: 10.1111/j.1556-4029.2010.01671.xSave Citation »Export Citation »E-mail Citation »

                                                                                        The results of this investigation of the effect of case context on the evaluation of the strength of forensic DNA evidence suggest that an effect of context exists in criminal cases. Furthermore, this effect is stronger when the evidence is of weak or moderate value.

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                                                                                        Visual Communication

                                                                                        From the illustration of the crime scene to the visualization of marks and their comparison to impressions, every step of the forensic process can, in principle, be visually represented (with the notable exception perhaps of final inferences). Besides, graphical representation can be used to clarify relationships between entities and between spatial and temporal issues. While mock-ups and videotaping (i.e., bringing the scene to the courtroom) are treated in Use of New Technologies for Expert Evidence Presentation, graphics chosen to represent the experts’ findings are treated here. Tufte 2001 sets out the major rules of proper graphical representation. Otherwise, some research into graphical representations comes from the medical field. Garcia-Retamero, et al. 2010 shows that denominator neglect decreases when icons are used for illustration. Sloman, et al. 2003 suggests that base-rate neglect can be improved by nested diagrams, and Brase 2009 compares different graphical representations and their ability to improve Bayesian reasoning. Finally, Rossy and Ribaux 2012 investigates graphical representation of investigative elements. They show that the conception of link charts is subject to variations.

                                                                                        • Brase, Gary L. 2009. Pictorial representations in statistical reasoning. Applied Cognitive Psychology 23.3: 369–381.

                                                                                          DOI: 10.1002/acp.1460Save Citation »Export Citation »E-mail Citation »

                                                                                          Different representations are compared for their ability to simplify Bayesian reasoning. From this, inferences are drawn concerning the underlying cognitive mechanisms. This publication shows that all graphical representations are not equal and that iconic representation was more helpful than Venn diagrams for the task at hand.

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                                                                                          • Garcia-Retamero, Rocio, Mirta Galesic, and Gerd Gigerenzer. 2010. Do icon arrays help reduce denominator neglect? Medical Decision Making 30.6: 672–684.

                                                                                            DOI: 10.1177/0272989X10369000Save Citation »Export Citation »E-mail Citation »

                                                                                            One of the problems in risk assessment is denominator neglect; the focus is only on the successes and not on the number of attempts. This can be improved visually through graphics in which the total number of tested items is represented, with those successful ones being highlighted. This improves the understanding of frequencies.

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                                                                                            • Rossy, Quentin, and Olivier Ribaux. 2012. La conception de schémas relationnels en analyse criminelle: Au-delà de la maîtrise des outils. Revue internationale de criminologie et de police technique et scientifique 65.3: 345–362.

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                                                                                              Differences between creators of link charts in the context of crime analysis are explored. The use of entities and links varies between creators. The variations include the introduction of ambiguity and error into the representation.

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                                                                                              • Sloman, Steven A., David Over, Lila Slovak, and Jeffrey M. Stibel. 2003. Frequency illusions and other fallacies. Organizational Behavior and Human Decision Processes 91.2: 296–309.

                                                                                                DOI: 10.1016/S0749-5978(03)00021-9Save Citation »Export Citation »E-mail Citation »

                                                                                                Base-rate neglect leads decision makers to base their decision solely on the evidence and to ignore prior probabilities. This can be improved upon by a visual device: nested diagrams. These illustrate the probabilities before and after the adduction of evidence.

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                                                                                                • Tufte, Edward R. 2001. The visual display of quantitative information. 2d ed. Cheshire, CT: Graphics.

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                                                                                                  Tufte describes the criteria for graphical excellence (“the efficient communication of complex quantitative ideas”). He conclusively shows how the visual representation of data can aid comprehension. On the other hand, a whole chapter is dedicated to graphics that will convey (unintentionnally perhaps) untrue states of nature.

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                                                                                                  Poor Communication as a Cause of Wrongful Convictions

                                                                                                  When expert witnesses fail to express their results properly, or when fact finders misunderstand them, the consequences for the accused can be dire. A body of research based on exoneration data suggests that forensic science sometimes plays a critical role in the conviction of the innocent. One aspect of this problem is bad communication between the expert witness and the court (Garrett and Neufeld 2009). Historically, People v. Collins is one of the first cases in which bad communication of probabilistic data led to a questionable verdict. Many decades later, the Schiedam murder case, analyzed in van Koppen 2008, rocked the Netherlands and many other inquisitorial jurisdictions. The Farah Jama case in Australia served as a stern reminder of the dangers of lacking transparency when communicating scientific findings in court. In R. v. Clark, a woman was convicted for the murder of her two sons based on statistical computations that later proved to be incorrect; the Royal Statistical Society distanced itself explicitly from the evidence presented in court, and the case is still considered an example of bad use of statistical data in court. Lucia de Berk was a nurse who got convicted for killing her patients on the basis of statistical and toxicological evidence that later proved to be unsound. Interestingly, in these two cases (Sally Clark, Lucia de Berk), the misuse of scientific evidence was (at least partly) attributed to the fact that the experts had not received from the appointing authority all the information needed to assess the evidence properly. Finally, the Oberlandesgericht (OLG) Frankfurt case should serve as a warning to all expert witnesses that they can be held liable if they neglect the duties of their profession when communicating their findings to the court.

                                                                                                  • Garrett, Brandon L., and Peter J. Neufeld. 2009. Invalid forensic science testimony and wrongful convictions. Virginia Law Review 95.1: 1–97.

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                                                                                                    Seminal study that addresses the role of scientific evidence in wrongful convictions in the United States. This is a reference written by two of the major scholars in the field.

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                                                                                                    • Honourable F. H. R. Vincent, inquiry into the circumstances that led to the wrongful conviction of Mr Farah Abdulkadir Jama, Report, Victorian Government, 2010.

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                                                                                                      Illustrates one fundamental problem in communicating scientific findings in the courtroom: the lack of transparency concerning the limits of the analyses and interpretations carried out. In this case, the DNA evidence was presented in such a way that it excluded any risk of contamination, which turned out to be the exact problem in the case.

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                                                                                                      • Oberlandesgericht (OLG) Frankfurt, 02.10.2007-19 U 8/07.

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                                                                                                        Decision holding an anthropological expert liable for causing the wrongful conviction of Donald Stellwag, after he testified that it was “almost 100 percent” certain that the accused was the culprit. This implied certainty, whereas the written opinion contained the sentence “very high probability”; furthermore, this high probability was his subjective estimate and did not rest on any hard data, which was not clarified for the court. A rare instance of a court in Continental Europe opining as to the required presentation format of scientific results.

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                                                                                                        • People v. Collins. 438 P. 2d 33 (68 Cal. 2d 319 1968).

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                                                                                                          In this reference case from California, a couple was convicted on the basis of a statistical analysis that was flawed and that was presented to the court in a manner that exaggerated the value of the evidence against the accused (an error called a “prosecutor’s fallacy”). The conviction was later quashed.

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                                                                                                          • R. v. Clark. EWCA Crim. 1020, 11 April 2003.

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                                                                                                            Sally Clark was convicted of murder after her first two children had died with no apparent medical reason. Her conviction, later overturned, was based largely on the statistical evidence presented by a pediatrician who miscalculated the probability that two siblings would both die of sudden infant death syndrome. In this judgment, the court of appeal quashed the convictions and explained why it deemed them to be unsafe.

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                                                                                                            • Rapport Commissie evaluatie afgesloten strafzaken inzake mevrouw de B. October 29, 2007. (Posthumus report).

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                                                                                                              Published after the conviction for multiple murders of nurse Lucia de Berk, this report recommended that the case be reopened. The accused, later exonerated, had been prosecuted for having poisoned her patients with digoxin, on the basis of scientific evidence whose weight was misunderstood by the fact finders.

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                                                                                                              • Van Koppen, Peter J. 2008. Blundering justice. In Serial murder and the psychology of violent crimes. Edited by Richard N. Kocsis, 207–228. Totowa, NJ: Humana.

                                                                                                                DOI: 10.1007/978-1-60327-049-6_12Save Citation »Export Citation »E-mail Citation »

                                                                                                                A summary in English of the Schiedam Park murder case, which started in 2000 in the Netherlands. Mainly caused by the false confession of the prime suspect, this miscarriage of justice also sheds light on serious communication problems between the experts, the prosecution and the courts around forensic DNA analysis.

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                                                                                                                Use of New Technologies for Expert Evidence Presentation

                                                                                                                Photography has long been used to bring the crime scene into the courtroom. Nowadays, videotaping and virtual reconstructions, sometimes even interactive, are used for the same purpose. While Schofield 2007 highlights the promises and expected pitfalls of the use of modern technology in the courtroom (as well as its uses at other stages of the forensic process), Feigenson 2010 highlights the dearth of studies concerning the improvement in comprehension these methods promise as well as the lack of agreement between existing studies. Kassin and Garfield 1991 are among the forerunners of experiments on the impact of videotaped crime scenes (not observing any effect of the showing of the video versus not showing a video). Douglas, et al. 1997 contradicts their results. The impact of computer animation was evaluated by Kassin and Dunn 1997, who clearly highlight the dual nature of visualization. Indeed, while such evidence can improve understanding and memory, it can also strongly influence the decision maker. Bennett, et al. 1999, however, observes no impact of computer animations. Tait 2007 reiterates the important point that the impact of visual aid will depend on the goal pursued by those using it.

                                                                                                                • Bennett, Robert B. J., Jordan H. Leibman, and Richard E. Fetter. 1999. Seeing is believing; or is it? An empirical study of computer simulations as evidence. Wake Forest Law Review 34:257–294.

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                                                                                                                  Presented with animations in the case of an accident, mock jurors were not swayed: they rendered the same number of guilty verdicts and awarded the same amount of damages to the victim when shown an animation as when an expert described the accident to them.

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                                                                                                                  • Douglas, Kevin S., David R. Lyon, and James R. Ogloff. 1997. The impact of graphic photographic evidence on mock jurors’ decisions in a murder trial: probative or prejudicial? Law and human behavior 21:485–501.

                                                                                                                    DOI: 10.1023/A:1024823706560Save Citation »Export Citation »E-mail Citation »

                                                                                                                    In mock jurors, the proportion of guilty verdicts doubles when the picture of a murder victim is shown (whether in color or black and white) versus when no photographs are shown.

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                                                                                                                    • Feigenson, Neal. 2010. Visual evidence. Psychonomic Bulletin and Review 17:149–154.

                                                                                                                      DOI: 10.3758/PBR.17.2.149Save Citation »Export Citation »E-mail Citation »

                                                                                                                      A critical review of different types of visual evidence and of different effects on decision making. The relative dearth and contradictory nature of the results is highlighted, and avenues for research are brought forward.

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                                                                                                                      • Kassin, Saul M., and Meghan A. Dunn. 1997. Computer-animated displays and the jury: Facilitative and prejudicial effects. Law and human behavior 21:269–281.

                                                                                                                        DOI: 10.1023/A:1024838715221Save Citation »Export Citation »E-mail Citation »

                                                                                                                        This study suggests the possibility of prejudicial effects of partisan animated displays. However, when nonpartisan presentation formats are used, beneficial effects are obtained: jurors then render judgments more in agreement with the evidence than if no animations are used.

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                                                                                                                        • Kassin, Saul, and David A. Garfield. 1991. Blood and guts: General and trial-specific effect of videotaped crime scenes on mock jurors. Journal of Applied Social Psychology 21:1459–1472.

                                                                                                                          DOI: 10.1111/j.1559-1816.1991.tb00481.xSave Citation »Export Citation »E-mail Citation »

                                                                                                                          There was no difference in the proportion of guilty verdicts, whether groups of mock jurors had seen a video of the victim, a video of a victim of another crime, or no video. However, the standard of proof seems to be lowered when a video is shown.

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                                                                                                                          • Schofield, Damian. 2007. Animating and interacting with graphical evidence: Bringing courtrooms to life with virtual reconstructions. In Computer graphics, imaging and visualisation. Proceedings of an international conference on computer graphics, imaging and visualization, Bankgok, 14–17 August 2007. Edited by Ebad Banissi, Muhammad Sarfraz, and Natasha Dejdumrong, 321–328. Los Alamitos, CA: IEEE Computer Society.

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                                                                                                                            Describes how different kinds of 3D reconstructions can be integrated into the forensic process. The author details the promise these methods hold for the improvement in communication but also during the investigation, particularly when complex temporal and spatial data are to be conveyed.

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                                                                                                                            • Tait, David. 2007. Rethinking the role of the image in justice: Visual evidence and science in the trial process. Law, Probability and Risk 6:311–318.

                                                                                                                              DOI: 10.1093/lpr/mgm040Save Citation »Export Citation »E-mail Citation »

                                                                                                                              After presenting visualization as both an instrument of logic and a tool of persuasion, the author describes some visualization tools that help jurors understand and memorize evidence. He concludes with a call for more empirical research in the field.

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                                                                                                                              How to Improve Statements Made by Forensic Scientists

                                                                                                                              Proposals aiming at clarifying statements made by forensic scientists are quite diverse, and scholars have explored several possibilities over the years. Edmond, et al. 2014 suggests a clearer way of signaling the meaning of a match. This is also what Rudram 1996 aims at in proposing a qualitative expression of probability. The classic reference for qualitative scales in reporting is Evett 1998. In a novel approach to forensic science, Howes, et al. 2014 uses different metrics to assess the reading difficulty of reports and of conclusions (Howes, et al. 2013). All of these writings suggest that better statement writing will improve the use of forensic science in the judicial context. Finally, improving the fact finder’s understanding of expert reports through education is the subject of Goodman-Delahunty and Hewson 2010.

                                                                                                                              • Edmond, Gary, Matthew B. Thompson, and Jason M. Tangen. 2014. A guide to interpreting forensic testimony: Scientific approaches to fingerprint evidence. Law, Probability and Risk 13:1–25.

                                                                                                                                DOI: 10.1093/lpr/mgt011Save Citation »Export Citation »E-mail Citation »

                                                                                                                                Separating the “match” decision from the assessment of the identification value of such a match, the authors suggest that introducing information on error rate into statements would aid juror comprehension.

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                                                                                                                                • Evett, Ian W. 1998. Towards a uniform framework for reporting opinions in forensic science casework. Science and Justice 38:198–202.

                                                                                                                                  DOI: 10.1016/S1355-0306(98)72105-7Save Citation »Export Citation »E-mail Citation »

                                                                                                                                  In the context of the evaluative framework of forensic science, Evett indicates clearly which elements must be present in a statement for the reader to follow the interpretation of the evidence.

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                                                                                                                                  • Goodman-Delahunty, Jane, and Lindsay Hewson. 2010. Improving jury understanding and use of expert DNA evidence. Australian Institute of Criminology.

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                                                                                                                                    Using an eighteen-minute tutorial on forensic DNA analysis and random match probability, jury understanding of DNA evidence has been found to improve. This improved understanding lowered trust in DNA as well as scientific evidence in general.

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                                                                                                                                    • Howes, Loene M., Roberta D. Julian, Sally F. Kelty, Nenagh Kemp, and Paul Kirkbride. 2014. The readability of expert reports for non-scientist report-users: Reports of DNA analysis. Forensic Science International 237:7–18.

                                                                                                                                      DOI: 10.1016/j.forsciint.2014.01.007Save Citation »Export Citation »E-mail Citation »

                                                                                                                                      A detailed analysis of Australian expert reports concerning issues such as the lexical density, reading ease, and required grade level for reading the reports. Overall, these reports were deemed somewhat difficult to read, and improvements are proposed.

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                                                                                                                                      • Howes, Loene M., Paul Kirkbride, Sally F. Kelty, Roberta D. Julian, and Nenagh Kemp. 2013. Forensic scientists’ conclusions: How readable are they for non-scientist report-users? Forensic Science International 231:102–112.

                                                                                                                                        DOI: 10.1016/j.forsciint.2013.04.026Save Citation »Export Citation »E-mail Citation »

                                                                                                                                        An assessment of conclusions in a proficiency test on glass analysis, using standard readability measures, shows that these conclusions would be difficult to read for an audience without some tertiary scientific education. Concrete suggestions for improvements are offered.

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                                                                                                                                        • Rudram, D. A. 1996. Interpretation of scientific evidence. Science and Justice 36:133–138.

                                                                                                                                          DOI: 10.1016/S1355-0306(96)72587-XSave Citation »Export Citation »E-mail Citation »

                                                                                                                                          Rudram suggests a published and available hierarchy of qualitative expressions of probability that are common to all subjects in forensic science. He also suggests including the hierarchy used in reports for clarity.

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