A Bayesian Model of the Litigation Game

Over a century ago, Oliver Wendell Holmes invited scholars to look at law through the lens of probability theory: ‘The prophecies of what the courts will do in fact, and nothing more pretentious, are what I mean by the law'. But Holmes himself, and few others, have taken up this intriguing invitation. As such, in place of previous approaches to the study of law, this paper presents a non-normative, mathematical approach to law and the legal process. Specifically, we present a formal Bayesian model of civil and criminal litigation, or what we refer to as the ‘litigation game'; that is, instead of focusing on the rules of civil or criminal procedure or substantive legal doctrine, we ask and attempt to answer a mathematical question: what is the posterior probability that a defendant in a civil or criminal trial will be found liable, given that the defendant has, in fact, committed a wrongful act?