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Rape, Murder, and Formalism: What Happens If We Define Mistake of Law?

98 Pages Posted: 28 Sep 2000  

Gerald Leonard

Boston University School of Law

Date Written: September 7, 2000


The criminal law maxim "ignorance of the law is no excuse" represents a broad doctrine of strict liability in an area of law that usually insists on a culpable state of mind as a prerequisite for liability. For that reason, many scholars have attacked the harsh mistake-of-law rules as incompatible with basic principles of culpability. Other scholars have come to the defense of the maxim, and courts have adhered to it quite strongly even as the list of exceptions to the maxim has slowly grown. Oddly enough, however, this debate has proceeded without a definition of mistake of law. Distinguishing mistake of law, which generally does not excuse, from mistake of fact, which generally does, has proven difficult for scholars and judges alike, with the result that no serious effort to provide a definition of that distinction has yet been made. This article tries to fill that gap. It first defines the distinction by emphasizing law's status as a special system of linguistic meaning within the larger world of fact. It then uses that definition to argue that some orthodox categories of criminal law, particularly "mistake of non-criminal law" and "unreasonable mistake of fact," are empty concepts that serve only to obfuscate the line between mistake of law and mistake of fact, obscure the conflicts between at least two competing traditions of criminal intent, and thus impede a principled approach to the problem of whether and when ignorance of the law should excuse.

Suggested Citation

Leonard, Gerald, Rape, Murder, and Formalism: What Happens If We Define Mistake of Law? (September 7, 2000). Boston Univ. School of Law Working Paper No. 00-09. Available at SSRN: or

Gerald Leonard (Contact Author)

Boston University School of Law ( email )

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Boston, MA 02215
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