Relative Plausibility and its Critics

Abstract

Within legal scholarship there is a tendency to use (perhaps overuse) "paradigm shift" in ways far removed from the process famously described by Thomas Kuhn. Within the field of evidence, however, a phenomenon very similar to a paradigm shift, in the Kuhnian sense, is occurring. Although not on the scale of the transformation from Newtonian to Einsteinian physics or other tectonic shifts in science, the best understanding of juridical proof is shifting from probabilism to explanationism. For literally hundreds of years, proof at trial was assumed to be probabilistic. This assumption was given sustained scholarly attention and support beginning with the 1968 publication of John Kaplan's path-breaking article that generated a rich literature explaining virtually all aspects of juridical proof as probabilistic, from the basic nature of relevancy through the processing of information to the final decision about the facts. Although probabilism quickly became the dominant paradigm, some analytical difficulties were detected quite early ("anomalies" or "irritants" in the words of Kuhn), beginning with L. Jonathan Cohen's demonstration of certain proof paradoxes. These were extended by Ronald Allen, who also demonstrated the incompatibility of Bayesian reasoning with trials and proposed an analytical alternative. Again a complex literature ensued with the defenders of the dominant paradigm attempting to explain away the anomalies or to shield the probabilistic paradigm from their potentially corrosive effects (in what in fact on a very small scale is precisely what Kuhn explained and predicted with respect to paradigm shifts in science). Over the last two decades, these anomalies have become too irritating to ignore, and the strengths of the competing paradigm involving explanatory inferences (referred to as the relative plausibility theory) have become too persuasive to dismiss. Thus the paradigm shift that the field is now experiencing. We provide here a summary of the relative plausibility theory and its improvement on the probabilistic paradigm. As Kuhn noted, not everybody gets on board when paradigms shift; there are holdouts, dissenters, and objectors. Three major efforts to demonstrate the inadequacies of relative plausibility have recently been published. We analyze them here to demonstrate that their objections are either misplaced or unavailing, leaving relative plausibility as the best explanation of juridical proof. It is interesting to note that two of the three critiques

Neural support for contributions of utility and narrative processing of evidence in juror decision making

“…Narrative models, by contrast, propose that evidence integration relies on the extent to which the evidence can be assembled into a cohesive, compelling, and credible story (1,12). For jury decisions, narrative explanations are based on the extent to which the total body of information about a case can be structured into a coherent account and how closely the competing narratives offered by prosecution and defense match the juror's background knowledge, experience, and beliefs (10,(13)(14)(15). Although most fields have relied heavily on the utility model, the narrative framework has been widely adopted for trial practice (16) while utility models play a role primarily in theoretical explanations.…”

Probability reasoning in judicial fact-finding

“…An informal introduction to the debate can be found in Park et al (2010). Formally developed arguments for IBE in fact-finding are found in Allen and Pardo (2019b) and Allen and Stein (2013). For counter arguments and support for probabilistic reasoning see Nance (2016), Cheng (2013), Kaye (2016), Schwartz and Sober (2017), Clermont (2015), Friedman (1997) and Sullivan (2019).…”

“…The key difficulty with IBE, in any context, is understanding what ‘explains better than’ or ‘is more compelling than’ really means. Lipton’s shift in terms to ‘loveliness’ does not help in this respect; nor does the term ‘relative plausibility’, used by Allen and Pardo (2019b), help. And the judgment in Re A gives no guidance either.…”

“…Leading proponents of IBE advocate finding facts with a preponderance-style standard of proof and a naive or one-step IBE method. For example, Pardo (2013) and Allen and Pardo (2019b) offer the following example.[S]uppose a plaintiff offers a story that a reasonable jury concludes is 0.4 likely and the defendant offers a story that the jury concludes is 0.2 likely. The ‘greater than 0.5’ standard implies that the plaintiff should lose—even though the plaintiff’s account is twice as likely to be true as the defendant’s alternative account.…”

Normative decision analysis in forensic science

“…Evidence and decision-making are prevalent topics in legal scholarship, with a longstanding history, diverse methodological perspectives and concurrent theoretical accounts. 1 Despite the multitude of approaches covering normative, descriptive, prescriptive and interpretative views, certain concepts centering around decision-making in the law and adjacent areas, in particular criteria or rules of decision, remain controversial (e.g., Allen and Pardo, 2018). This poses a challenge to interdisciplinary exchange.…”