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Mistake of Law Defense

Mistake of Law is not a valid defense to a general intent crime. Even if the defendant’s mistake was reasonable, mistake of law is not a valid defense. (See People v. Marrero). The only exception is if a statute proscribing the defendant’s conduct has not been reasonably made available or if the defendant recently relied on a statute or judicial decision that was recently held unconstitutional.

However, under a specific intent crime, the defendant’s mistake of law is a valid defense whether reasonable or unreasonable. (See Cheek v. United States).

Compare to Mistake of Fact Defense

More Helpful Information: List of General Intent and Specific Intent Crimes

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Mistake of Fact Defense

Under the Common Law, if the crime only requires general intent, the defendant’s mistake must be reasonable for mistake of fact to be a valid defense. If the crime is a specific intent crime, the defendant’s mistake can be reasonable or unreasonable. This reasonableness is first a legal conclusion, then it goes to the jury to determine whether or not the mistake was reasonable.

Under the MPC Section 2.04, the defendant’s mistake must go towards negating the mens rea required for the crime. If the crime only requires general intent, the mens rea is going to default to recklessness.

See Regina v. Prince for an example of mistake of fact.

Compare to Mistake of Law

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Regina v. Prince, L.R. 2 Cr. Cas. Res. 154 (1875)

Case Name: Regina v. Prince
Citation: L.R. 2 Cr. Cas. Res. 154 (1875)

Facts: Defendant was convicted of taking an unmarried girl under 16 years out of the possession and against the will of her father (a misdemeanor). The jury found that the girl had told the defendant she was 18, the defendant honestly believed the statement, and his belief was reasonable.

Defendant’s argument: The statute has a requirement read into it that the prosecution must prove that the defendant believed the girl he had taken was over 16.

State’s argument: The statute does not require this proof. The act of taking a girl out is wrong in and of itself – that is the mens rea. It does not matter that he thought the girl was older. Just like it would not matter whether he knew or did not know whether she is under 16. However, it would have mattered if he did not know the girl was in the custody of her father.

Holding: Conviction affirmed.

Reasoning: The court interpreted the statute to require a strict liability application. The Common Law does not allow defenses to strict liability.

Dissent: The defendant had reasonable ground for believing what the girl told him and had what she said been true, he would not have done the act (no mens rea). “a mistake of facts, on reasonable grounds…is an excuse” (if, had the facts been true, he would not have been guilty) that is implied in every criminal charge and enactment in England.