Teaching an Application of Bayes' Rule for Legal Decision-Making: Measuring the Strength of Evidence

Although Bayesian methodology has become a powerful approach for describing uncertainty, it has largely been avoided in undergraduate statistics education. Here we demonstrate that one can present Bayes' Rule in the classroom through a hypothetical, yet realistic, legal scenario designed to spur the interests of students in introductory- and intermediate-level statistics classes. The teaching scenario described in this paper not only illustrates the practical application of Bayes' Rule to legal decision-making, but also emphasizes the cumulative nature of the Bayesian method in measuring the strength of the evidence. This highlights the Bayesian method as an alternative to the traditional inferential methods, such as p value and hypothesis tests. Within the context of the legal scenario, we also introduce DNA analysis, implement a modified version of Bayes' Rule, and utilize Bayes' Factor in the computation process to further promote students' intellectual curiosities and incite lively discussion pertaining to the jury decision-making process about the defendant's status of guilt.