Interpretation of statistical evidence in criminal trials: The prosecutor's fallacy and the defense attorney's fallacy.

Thompson, William C.; Schumann, Edward L.

doi:10.1007/bf01044641

Cited by 319 publications

(225 citation statements)

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“…Gigerenzer and Hoffrage (1995;see also, e.g., Cosmides & Tooby, 1996) demonstrated that Bayesian answers can be elicited with the use of a frequency format for both the information and the question asked. Moreover, Thompson and Schumann (1987) showed that frequency formats reduced the number of inverse fallacies committed. A probability presentation format might increase the use of heuristics, but that still does not explain why most people tend to commit the inverse fallacy rather than use another heuristic (e.g., the joint-occurrence algorithm described in Figure 1).…”

Section: Theoretical Implicationsmentioning

confidence: 99%

The inverse fallacy: An account of deviations from Bayes’s theorem and the additivity principle

2002

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In judging posterior probabilities, people often answer with the inverse conditional probability-a tendency named the inverse fallacy. Participants (N = 45) were given a series of probability problems that entailed estimating both p(H | D) and p(,H | D). The findings revealed that deviations of participants' estimates from Bayesian calculations and from the additivity principle could be predicted by the corresponding deviations of the inverse probabilities from these relevant normative benchmarks. Methodological and theoretical implications of the distinction between inverse fallacy and base-rate neglect and the generalization of the study of additivity to conditional probabilities are discussed.

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Section: Theoretical Implicationsmentioning

confidence: 99%

The inverse fallacy: An account of deviations from Bayes’s theorem and the additivity principle

2002

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“…It is possible that participants in this study experienced difficulty comprehending the DNA match probability provided, and preexisting beliefs regarding DNA may have encouraged the guilty verdict. A third reason could be that the probability of the defendant's guilt was determined by or based on the rarity of the DNA match statistic provided in the expert testimony and subsequently the strengths of other evidence was ignoredotherwise known as the "prosecutor's fallacy" (Thompson & Schumann, 1987). This type of fallacious reasoning occurs where jurors (and sometimes lawyers) interpret the random match probability as the probability of the defendant being innocent (Koehler, 2013).…”

Section: Discussionmentioning

confidence: 99%

The Persuasive Powers of DNA: An Experimental Study in Perceptions of Expert Evidence

2014

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Abstract-This article presents the results of an experimental study where mock-jurors were tasked with interpreting the presentation of DNA evidence. The 200 university student participants were exposed to one of five murder scenarios where the information about the DNA evidence was manipulated. The results showed that participants were more likely to convict when the DNA match statistic was presented as a probability (0.1%) and focused on the defendant, less likely to convict when it was presented as a frequency (1 in 1,000) and focused on a broader reference group, and even less likely in the control scenario with no DNA evidence. The forensic knowledge of participants was also explored, and more than three-quarters demonstrated reasonable understanding of the individuating capacity of DNA evidence. Participants recognized that while DNA has the capacity to determine guilt, it is insufficient on its own to convict or acquit. The implications for the presentation of expert testimony and judicial instruction are canvassed, and the broader ramifications for the education of jurors and legal personnel are discussed.Index Terms-DNA evidence, expert evidence, juror decisionmaking, match statistics I. INTRODUCTION HE forensic application of DNA has increased the frequency of criminal investigations that rely on biological material for identification purposes (Goodman-Delahunty & Tait, 2006) and this impact clearly carries through into the adjudicative setting (Amorim, 2012;Briody, 2003;. Due to its use in violent and high profile cases, and its role in overturning wrongful convictions, DNA analysis has been considered the great panacea for criminal investigations and court proceedings (Butler, 2001;Cooper, 2012; Kirby, 2010;Lincoln & Wilson, 2005;Lynch, 2013). It was once characterized in a It is, of course, difficult to argue against the power of DNA to incriminate the guilty, or deny its crucial role in exculpating the innocent, but like all powerful tools it has the capacity to produce undesirable consequences (Edmond, 2011; GoodmanDelahunty & Tait, 2006; Kirby, 2010;Langdon & Wilson, 2005;Lynch, 2013;McCartney, 2006). In the wake of the claim last century that little is known "about how laypersons respond to DNA evidence" (National Research Council, 1996), the body of research in this area has expanded significantly, providing knowledge about the weight that legal decision makers assign to it in forensic settings (Briody, 2003; GoodmanDelahunty & Hewson, 2010;Goodman-Delahunty & Wakabayashi, 2012;Findlay, 2008;Koehler, 2001;Koehler & Macchi, 2004;Kruse, 2012;Lynch, 2013;Smith & Bull, 2012;Smith, et. al., 2011;Wheate, 2006;.Studies in Australia demonstrate that there is potential to overly rely on DNA (Briody, 2003;. In one jurisdiction, it was found that cases of murder and sexual assault that include DNA have a higher likelihood of going to trial and a higher likelihood of securing a conviction than do cases without this type of evidence (Briody, 2003;. Such empirical studies raise serious questions about how ju...

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“…As Koehler and Saks (1991, p 371) note: "Where presumptions exist, they should be provided by the law, not by expert witnesses." Using only the likelihood ratio from the forensic anthropological evidence should protect the expert from this error, but unfortunately it is all too easy for the likelihood ratio to be misinterpreted by "transposing" the conditioning (Thompson and Schumann, 1987;Evett, 1995;National Research Council Committee on DNA Technology in Forensic Science, 1996;Foreman et al, 2003). Evett (1995, p 129) gives a clear illustration of a transposed conditional probability:…”

Section: More On Priors and The Problem Of Transposed Conditionals Inmentioning

confidence: 99%

“…The prosecutor would never have been asked to prosecute a case based on an identification which was as likely to be correct as incorrect. This form of transposition is referred to as the "prosecutor's fallacy" (first named so by (Thompson and Schumann, 1987)) because that is the usual source for the error.…”

Section: More On Priors and The Problem Of Transposed Conditionals Inmentioning

confidence: 99%

Bayes in biological anthropology

Konigsberg

Frankenberg

2013

American J Phys Anthropol

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In this article, we both contend and illustrate that biological anthropologists, particularly in the Americas, often think like Bayesians but act like frequentists when it comes to analyzing a wide variety of data. In other words, while our research goals and perspectives are rooted in probabilistic thinking and rest on prior knowledge, we often proceed to use statistical hypothesis tests and confidence interval methods unrelated (or tenuously related) to the research questions of interest. We advocate for applying Bayesian analyses to a number of different bioanthropological questions, especially since many of the programming and computational challenges to doing so have been overcome in the past two decades. To facilitate such applications, this article explains Bayesian principles and concepts, and provides concrete examples of Bayesian computer simulations and statistics that address questions relevant to biological anthropology, focusing particularly on bioarchaeology and forensic anthropology. It also simultaneously reviews the use of Bayesian methods and inference within the discipline to date. This article is intended to act as primer to Bayesian methods and inference in biological anthropology, explaining the relationships of various methods to likelihoods or probabilities and to classical statistical models. Our contention is not that traditional frequentist statistics should be rejected outright, but that there are many situations where biological anthropology is better served by taking a Bayesian approach. To this end it is hoped that the examples provided in this article will assist researchers in choosing from among the broad array of statistical methods currently available. Am J Phys Anthropol 57: 2013. V C 2013 Wiley Periodicals, Inc."The Bayesian approach can have a clarifying effect on one's thinking about evidence." (Koehler and Saks, 1991, p 364) Traditional training in statistical methods for those who go on to become practicing biological anthropologists has focused primarily on classical hypothesis testing. This is apparent in both textbooks geared toward anthropologists in general (Thomas, 1986;Madrigal, 1998;Bernard, 2011) and specialized texts for biological anthropologists (Slice, 2005;D'Aoãut and Vereecke, 2011). While Bayes' Theorem may be mentioned in passing in introductory statistics courses, this is typically restricted to examples of such limited interest that the student has little motivation to recall the theorem, and even less motivation to assume that there may be future value in having learned about Bayes' Theorem. In Bayesian terms, the prior probability that the student will retain Bayes' Theorem is quite low. In contrast, the student and eventual practitioner is likely to learn about confidence intervals, Type I and Type II errors in hypothesis testing, and P-values, and to blithely assume that what they have learned represents the near totality of what is available and useful within modern statistical practice. This represents an unfortunate omission of Ba...

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Interpretation of statistical evidence in criminal trials: The prosecutor's fallacy and the defense attorney's fallacy.

Cited by 319 publications

References 38 publications

The inverse fallacy: An account of deviations from Bayes’s theorem and the additivity principle

The inverse fallacy: An account of deviations from Bayes’s theorem and the additivity principle

The Persuasive Powers of DNA: An Experimental Study in Perceptions of Expert Evidence

Bayes in biological anthropology

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