Law Enforcement Costs and Legal Presumptions

We study and compare law enforcement costs under two alternative burden of proof rules with the objective of reducing crime to a target level. We show that presuming innocence rather than guilt has a cost advantage, mainly due to lower costs of preventing collusion between law enforcers and criminals. This conclusion may change if law enforcers are incorruptible or if resources to motivate corruptible law enforcers are limited. We identify the strengths and weaknesses of the two burden of proof rules in terms of components of law enforcement costs such as ``information gathering" costs, ``collusion prevention" costs, and (when the potential offender is an official) ``agent compensation" costs.