Optimal Preventive Law Enforcement and Stopping Standards

Preventive law enforcement increases social welfare by hindering the infliction of criminal harm, but produces inconvenience costs to the general public, because it requires interfering with the acts of innocents as well as attempters. This article shows that the optimal amount of investment in preventive enforcement is greater than that which maximizes deterrence, but, smaller than that which minimizes criminal harm. Thus, ignoring preventive benefits and/or inconvenience costs results in an inefficient investment portfolio over enforcement methods, and in a predictable manner. Moreover, it is possible for welfare to have multiple local maxima where one leads to `high deterrence/low prevention' and one leads to `low deterrence/high prevention'. Thus, a small increase in inconvenience costs can cause the optimal scheme to switch from the latter scheme to the former scheme, and necessitate large reductions in preventive enforcement. Additionally, stopping standards, which determine the threshold suspicion required to trigger a stop, are tools that can be used to optimally trade-off the costs and benefits associated with preventive enforcement. The optimal investigation standard is weaker than its analog in the trial context, namely standards of proof, which generally require preponderance of the evidence in civil trials and proof beyond a reasonable doubt in criminal trials. Finally, suspicionless stops can be optimal in a variety of circumstances, and are more likely optimal when enforcers perform poorly in forming suspicions; inconvenience costs are small; the population is unresponsive to deterrence measures; and the attempt rate is high