Should Legal Empiricists Go Bayesian? (original) (raw)
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Annual Review of Statistics and Its Application, 2016
Although the last forty years has seen considerable growth in the use of statistics in legal proceedings, it is primarily classical statistical methods rather than Bayesian methods that have been used. Yet the Bayesian approach avoids many of the problems of classical statistics and is also well suited to a broader range of problems. This paper reviews the potential and actual use of Bayes in the law and explains the main reasons for its lack of impact on legal practice. These include misconceptions by the legal community about Bayes' theorem, over-reliance on the use of the likelihood ratio and the lack of adoption of modern computational methods. We argue that Bayesian Networks (BNs), which automatically produce the necessary Bayesian calculations, provide an opportunity to address most concerns about using Bayes in the law.
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Legal Probabilism is the view that mathematics, and probability theory in particular, can be used to explicate the standard of legal decisions. While probabilistic tools are sometimes used in courtrooms, the construction of a general model of evidence evaluation remains a challenge. Conceptual diffi culties facing Legal Probabilism include the diffi culty about conjunction, the diffi culty about corroboration and the gatecrasher paradox. These problems need to be addressed before we construct a general model. In this survey we discuss the three diffi culties and present some theories proposed as their solutions.
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SSRN Electronic Journal, 2003
Will there ever be a Nobel Prize in law? Professor Ulen uses this question as a framework for discussing the current state of legal scholarship and the trend toward making legal scholarship more "scientific." First, Professor Ulen discusses the meaning of "science" and the scientific method, and summarizes the various theories that have developed over time to verify, modify, or reject scientific paradigms. Next, he considers whether or not the study of law is a science. All sciences share core theoretical beliefs that allow for the international study and dissemination of scientific information, and that will produce similar results, regardless of where they are applied. These theories are then examined and tested using empirical research. Although law has no such set of core theoretical beliefs, there is a growing body of empirical research in the law. Professor Ulen believes that interest in empiricism is growing in the legal academy, and that empirical research can be very beneficial to both legal academics and practitioners. As the amount and breadth of legal empirical research increases, Professor Ulen posits that a core set of theoretical beliefs will emerge in the law, and that increased empiricism in the law is vital to the future of the law as a science.
Scientific Evidence and the Law: An Objective Bayesian Formalization
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We examine a long-standing research program in empirical Political Science, fact-pattern analysis (FPA). We connect FPA to definitions of legal rules in jurisprudence and positive political theory. Foundationally, theoretical treatments view rules as functions partitioning case spaces into equivalence classes. Connecting FPA to formal theory has two advantages: first, many elements of the traditional understanding of legal rules become interpretable in terms of FPA, and vice versa. Second, the methodological issues in empirical FPA become much clearer. In particular, the similarity between FPA and related work in artifical intelligence, expert systems, and machine learning becomes obvious. On this basis, following Kastellec 2005, we critique logit, probit, and disciminant analysis-based FPA as less likely to uncover interpretable legal rules than other techniques developed to induce decision trees from data. As noted by Kastellec, classification and regression trees (CART) appear particularly promising in the legal context. We note the possibility of applying CART-based FPA to many areas of the law, with potentially significant applications in legal education and legal practice. We then examine recent attempts to use FPA to uncover changes in "legal regimes." We suggest that CART could be employed more successfully in this task. We then examine attempts to use FPA in the long-standing "law vs. preferences" debate in Political Science. In our view, this debate as presently framed is unlikely to be productive. We illustrate our points with estimations using simulated data.