Avoidance, Errors and the Optimal Standard of Proof

Criminals often engage in costly avoidance to lower their probability of being detected and sanctioned. Such avoidance, in turn, affects the optimal enforcement policy. This paper studies the impact of avoidance on a specific type of enforcement policy - the standard of proof. We show that when avoidance is possible the optimal standard of proof is weaker than preponderance of the evidence. This stands in contrast to much of the literature, which shows that non-deterrence costs usually cause the standard of proof to be stronger than preponderance. Our results suggest that it is important not to ignore criminals' secondary behavior when determining the optimal standard of proof