§ 13.01 General Principles

§ 13.01 General Principles¹

[A] General Rule

"In determining whether a defendant's mistaken belief disproves criminal intent, the courts have drawn a distinction between mistakes of fact and mistakes [or ignorance²] of law."³ Specifically, the law treats mistakes of law more strictly—allows for exculpation of a defendant less readily—than mistakes of fact. Subject to very limited exceptions, the common law mistake-of-law rule is straightforward: ignorantia legis neminem excusat, or ignorance of the law is not an excusing defense.⁴ This "dogmatic common-law maxim"⁵ is deeply embedded in Anglo-American jurisprudence.⁶

It is also the case that ignorance or mistake of law only rarely serves as a basis for claiming that a defendant lacked the requisite mens rea defined in an offense. That is, neither knowledge nor recklessness or negligence as to whether conduct constitutes an offense, or as to its meaning, ordinarily is an element of that offense; therefore, it follows that there typically is no mens rea element in an offense capable of being negated by an actor's ignorance or mistake of law.

Put simply, once it is determined that a defendant is asserting a mistake of law, rather than mistake of fact, claim,⁷ the default legal position is simple: the defendant's mistake will not exculpate, subject to the few narrow exceptions described in this chapter.

[B] Rationale of the Rule

[1] Certainty of the Law

It has been said that the law is "definite and knowable."⁸ Therefore, it may be argued, there is no such thing as a reasonable mistake of law. Anyone who misunderstands the "definite and knowable" law has simply not tried hard enough to learn it and, consequently, is morally culpable for failing to know the law.

At common law, this claim might have had the ring of plausibility. The courts recognized few criminal offenses, and those that existed involved conduct malum in se. Few people could seriously allege surprise in learning that stealing another person's property, intentionally burning down another person's house, or unjustifiably taking another person's life, was illegal.

However, even at common law, the principle that laws were definite and knowable was sometimes a fiction. Criminal laws were not enacted by legislatures and published, as they are today. Instead, judges shaped the law on a case-by-case basis, which meant that the criminal law changed incrementally with each new decision. Moreover, the definitions of some common law offenses were not models of clarity.⁹

Whatever its plausibility centuries ago, the "definite and knowable" claim cannot withstand modern analysis. There has been a "profusion of legislation making otherwise lawful conduct criminal (malum prohibitum)."¹⁰ Therefore, even a person with a clear moral compass is frequently unlikely to realize that particular conduct is prohibited. Furthermore, many modern criminal statutes are exceedingly intricate. In today's complex society, therefore, an ordinarily law-abiding person can reasonably misunderstand the law or even fail to know of a particular penal law's existence.

[2] Avoiding Subjectivity in the Law

Jerome Hall once provided a more sophisticated explanation for the common law rule.¹¹ In stark contrast to the assertion that criminal laws are definite and knowable, Hall claimed that laws are "unavoidably vague" and that persons can "disagree indefinitely regarding the[ir] meaning." At some point, Hall reasoned, debate regarding the meaning of a law must end: certain competent officials and institutions, particularly courts, must determine its meaning. Their official declarations provide an objective definition of penal provisions. If mistake-of-law could excuse, Hall argued, the result would be that the law would lose its objective meaning; the law would mean whatever a person subjectively (and perhaps incorrectly) thought it meant.¹² Yet, a "legal order implies the rejection of such...