Crime Aggregation, Deterrence, and Witness Credibility *

Abstract

We present a model of criminal behavior and information aggregation in which the incentives to commit and to report crime are endogenous. An individual has several opportunities to commit crime, each of which associated with a witness with private reporting preferences and retaliation risk. We study how the mechanism used to map witness testimonies into verdicts affects criminal behavior and witness credibility when the punishment in case of conviction is large relative to the benefit of committing crime. We show that convicting defendants based on the probability that they have committed at least one crime reduces the maximal number of crimes but increases expected crime frequency and undermines the informativeness of witness testimonies. We characterize mechanisms that minimize the expected number of crimes subject to an upper bound on the fraction of wrongful convictions. The optimum is always attained by one of two aggregation rules discussed in legal scholarship.

Keywords: Information Aggregation, Soft Evidence, Deterrence, Adjudication Rule D82, D83, K42