Mistake and Mens Rea

Mistake and Mens Rea

Section 2.04(1)(a) answers the question of what a defendant's wrong belief is worth by sending the reader back to a question every prosecution already has to answer: did the defendant have the mental state the offense requires? On that view a mistake claim is a way of testing the prosecution's own proof, so it needs no separate theory of excuse.¹ This section develops the idea in two parts. The first is the rule that a mistake matters when, and only when, it negates a required mental state, and the second is the consequence for who must prove what at trial.

The Negation Principle

The operative text is short. Ignorance or mistake as to a matter of fact or law is a defense when it "negatives the purpose, knowledge, belief, recklessness or negligence required to establish a material element of the offense."² Three features of that language carry the analysis. The list of five mental states means the rule applies to whichever one the offense attaches to the element in question. A material element is a component of the offense's definition, such as the prohibited conduct, an attendant circumstance like the ownership of property, or a result, and the mistake must reach one of these. The words "fact or law" direct the reader to the effect the error has on the mental state, whether the defendant misjudged the world or misjudged a legal rule.

The rule is easiest to hold once you see that it adds nothing to the law of mens rea. A defendant cannot be convicted of an offense without the mental state that offense demands, and a mistake is one way of lacking it. The standard illustration is a diner who leaves a restaurant with an umbrella that he sincerely believes is his own, when it actually belongs to another patron. Larceny requires an intent to steal the property of another. Because the diner believes the umbrella is his, he does not have that intent, so an element of larceny is missing and he is not guilty of the offense.³ Nothing in this reasoning calls for a separate excuse; the offense as defined has simply not been committed, and the mistake is the reason the intent is absent.

The same logic reaches every offense that requires purpose, knowledge, or recklessness, because it would contradict itself to say that such an offense was committed by someone whose mistake rules out that very state of mind. The Code's provision therefore states what would be true even without it. Its practical value lies in correcting general formulas that make every mistake claim depend on one uniform condition without first asking what mental state the particular offense requires.⁴ For purpose, knowledge, and recklessness the mechanics are close to definitional. As to an attendant circumstance, each of these states requires that the defendant be aware that the fact exists or that there is a substantial probability it exists, so a defendant who honestly believes the white powder is salt does not know it is cocaine.⁵ Negligence works differently, and the question whether a belief must also be reasonable belongs to a later section of this chapter.⁶

Applied to the diner, step one identifies the intent to steal property of another as the mental state attached to the ownership element, and step two finds that his belief that the umbrella is his own cannot coexist with it. Step one deserves the most care, because the same belief can defeat the mental state of one offense and leave another untouched, and only the definition of the offense tells you which situation you are in.

One limit keeps the rule from rewarding deliberate ignorance. The Code treats a person who is aware of a high probability that a fact exists as knowing it, so a defendant cannot manufacture a mistake by declining to look.⁸ Without that limit, the easiest way to lack knowledge would be to avoid confirming a strong suspicion.

The illustrations so far involve mistakes about facts, but the rule applies equally to mistakes of law. The older view that a mistake of law never counted rested on a presumption that everyone knows the law, and a presumption of that kind sits poorly with the requirement that the prosecution prove every element, including any mental state attached to a legal matter.⁹ Many elements are legal concepts. Model Penal Code § 224.13, for instance, punishes a fiduciary who disposes of entrusted property in a manner he knows is unlawful and that risks loss to the beneficiary, an offense no one can commit culpably without some legal knowledge.¹⁰ The umbrella shows the same thing. A diner who takes it because he believes his earlier dealings with its owner made it his has made a mistake of law, yet he lacks the intent to steal the property of another just as surely as the diner who misjudged a fact.¹¹

A different kind of ignorance of the law leaves the mental state intact, and it is the one the old maxim describes. A diner who knows the umbrella belongs to someone else and takes it, protesting only that he did not realize taking it was a crime, has the intent to steal; his belief conflicts with no element, so there is nothing for it to negate.¹² Students lose points here when they treat ignorance that the conduct is criminal as a mistake that negates intent. The Code builds this boundary into its general rules: knowledge, recklessness, or negligence about whether conduct is an offense, or about the existence, meaning, or application of the law that defines the offense, is not an element unless the definition of the offense or the Code says so.¹³ Mistakes that concern criminality itself are taken up in the last section of this chapter.

Who Bears the Burden

The practice of calling a mental-state-negating mistake a defense probably follows from the fact that the evidence of it usually comes from the defendant, since it concerns what the defendant believed, as with the diner's reason for thinking the umbrella was his.¹⁵ The label describes who brings the evidence forward and says nothing about who must win the point. That second question has a firm answer, which is that the prosecution must disprove the mental-state-negating mistake beyond a reasonable doubt.¹⁶

The reason appears when the burden is placed on the defendant. If the diner had to prove his mistake, a jury that found the evidence of his honest belief evenly balanced would convict him, even though it had a reasonable doubt whether he intended to steal. The element of intent would then be treated as established by the defendant's failure to carry a burden, and the prosecution's own evidence would not have established it. Because the lack of mens rea means an element is unproved, the burden of disproving the mistake stays where the burden on every element sits.

The due process principle behind this appears in Mullaney v. Wilbur, where the Supreme Court measured a Maine rule requiring a murder defendant to prove that he acted in the heat of passion on sudden provocation against the requirement that the prosecution prove beyond a reasonable doubt every fact necessary to constitute the crime charged.¹⁷ That case involved provocation rather than mistake, so it serves here only as an analogy, but the logic transfers because the required mental state is itself an element. The older insanity decision in Davis v. United States rests on the same premise, the common-law view that a complete crime requires both a guilty will and a wrongful act.¹⁸

Treatment as part of the prosecution's case-in-chief is the general rule, and it has exceptions. In some codes a defendant's mistake of law operates as an affirmative defense, resting on a separate rule of law rather than on the elements, which fits the statutory route described at the start of this chapter.¹⁹ How a trial court must treat a mistake once the evidence raises it, including what the jury is told, comes up with the applications that follow.