Abstract

Attempts to establish a quantitative framework for thinking about the criminal justice system have been made at least since Kaplan’s influential 1968 article. Here I avoid the probabilistic approaches that Kaplan inspired and instead characterise the law’s underlying problem as one of measurement. I then exploit statistical techniques developed in recent years in other disciplines to evaluate systems that also face the challenge of ‘binary classification’ to solve it. This approach entails the mathematisation of the criminal justice system’s core epistemic concern of distinguishing the guilty from the innocent with Van Rijsbergen’s F-measure and empirical measurements of effectiveness. Once one adopts the perspective of a sovereign, it yields a meta-meta-epistemology that allows traditional arguments like those that refer to Blackstone’s ratio to be made rigorous. This provides a clearer relationship between values and policies and, in a narrowly epistemic sense, a complete answer to questions of evidence and procedure.