Insincere Evidence

61 Pages Posted: 18 Mar 2019 Last revised: 29 Oct 2019

See all articles by Michael D. Gilbert

Michael D. Gilbert

University of Virginia School of Law

Sean Sullivan

University of Iowa College of Law

Date Written: October 2019


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.

Keywords: insincere rule, burden of persuasion, deterrence, compliance

JEL Classification: K20,K41

Suggested Citation

Gilbert, Michael and Sullivan, Sean, Insincere Evidence (October 2019). 105 Virginia Law Review 1115 (2019), U Iowa Legal Studies Research Paper No. 2019-05, Virginia Public Law and Legal Theory Research Paper No. 2019-18, Virginia Law and Economics Research Paper No. 2019-07, Available at SSRN:

Michael Gilbert

University of Virginia School of Law ( email )

580 Massie Road
Charlottesville, VA 22903
United States

Sean Sullivan (Contact Author)

University of Iowa College of Law ( email )

Melrose and Byington
Iowa City, IA 52242
United States


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