MISTAKE OF LAW

The general rule is that ignorance of the law (or a mistake or misunderstanding about a law) is no defense. This is known so broadly, even outside the legal community, that it has achieved the status of cliché.

M.P.C. §2.02(9) expresses the general rule by using the concept of mens rea: with most offenses, the prosecution does not have to prove that the defendant had any mens rea with respect to the existence of the statute or its meaning or application.

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In other words, the mens rea terms in most statutes refer to the defendant’s state of mind with respect to the material elements of the offense (conduct, attendant circumstance, or result elements) and do not refer to the defendant’s awareness of the statute’s existence or meaning. We assume that defendants are aware of their legal duties and do not permit contrary evidence to serve as a defense.

The interesting issues involve the exceptions to the rule. Both the general rule and the exceptions are generally the same under both the common law and the Model Penal Code.

MISTAKE BY RELEVANT STATUTE

The first category of exceptions to the general "no defense" rule involves situations in which the statute defining the offense says that it (the statute) can be a defense.

(1) "Same Law Defense"

First, a statute may contain an explicit statement that a person is not guilty if she sincerely believed her conduct did not constitute an offense. This is the "same law" defense (Section 2.04(1)(b).

(2) "Different Law Defense:

Second, a statute may contain a reference to some other law (usually a non-criminal law), which means that the existence of the other law becomes an element of the statute, subject to the mens rea provisions contained in that statute (Section 2.04(1)(a)). This is the "different law" defense.

REASONABLE RELIANCE ON STATEMENTS OF OTHERS

The other main category of exceptions to the general "no defense" rule involves reasonable reliance on certain types of statements by others. Section 2.04(3) of the Model Penal Code provides as follows:

"A belief that conduct does not legally constitute an offense is a defense to a prosecution for that offense based upon such conduct when...(b) he acts in reasonable reliance upon an official statement of the law, afterward determined to be invalid or erroneous, contained in:

M.P.C. Section 2.04(3)(b)

CONCLUSION

The cliché that ignorance is no excuse, while expressing the general rule, requires several caveats associated with numerous exceptions.

For these and other topics, go to The Law School Experience.