Proving a violation of law is costly. Because of the cost, minor violations of law often go unproven and thus unpunished. To illustrate, almost everyone drives a little faster than the speed limit without getting a ticket. The failure to enforce the law against minor infractions is justifiable from a cost-benefit perspective. The cost of proving a minor violation—for example, a driver broke the speed limit by one mile per hour—outstrips the benefit. But it has the downside of underdeterrence. People drive a little too fast, pollute a little too much, and so on.
This paper explores how insincere rules, meaning rules that misstate lawmakers’ preferences, might reduce proof costs and improve enforcement. To demonstrate the argument, suppose lawmakers want drivers to travel no more than 55 mph. A sincere speed limit of 55 mph may cause drivers to go 65 mph, while an insincere speed limit of 45 mph may cause drivers to drop down to, say, 60 mph—closer to lawmakers’ ideal. Insincere rules work by creating insincere evidence. In the driving example, the insincere rule is akin to adding 10 mph to the reading on every radar gun.
We distinguish insincere rules from familiar concepts like over-inclusive rules, prophylactic rules, and proxy crimes. We connect insincere rules to burdens of persuasion, showing how they offset each other. Finally, we consider the normative implications of insincere rules for trials, truth, and law enforcement. The logic of insincerity is not confined to speed limits. The conditions necessary for insincerity to work pervade the legal system.