The Value of Truth and the Optimal Standard of Proof in Legal Disputes

Abstract

This article models the fact-finding process as one in which a defendant is accused of violating some legal standard (e.g., exceeding the speed limit). The fact finder cannot observe the actual behavior but observes some variable that is a noisy signal of the truth (e.g., the reading from a radar detector). From this signal it is possible to calculate the probability of guilt. The standard of proof (the minimal probability necessary to convict) that minimizes the expected cost of error is seen as a trade-off between the expected cost of false acquittals and convictions. A simple example shows that a clearer signal of truth (a more reliable radar detector) may not always lower error costs, because the utility of a fact-finding method depends also on the population of defendants and the standard of proof. These results clarify the source of disagreements over different fact-finding procedures. Copyright 1994 by Oxford University Press.