Y Mistake of Fact and Mistake of Law

Mistake of Fact - Common Law

Material element + mens rea required → MOF possible.
Immaterial element or strict liability → MOF barred.

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Mistake of fact is a defense only if it negates the mens rea for a material element.

When an element is immaterial (because of legislative intent, statutory structure, historical treatment, or because the mistake goes merely to the gravity of an already-illegal act), the offense is strict liability and no mistake-of-fact defense applies at all.

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Prince: D taking the girl was wrong in itself. Gravity of an already illegal act. Strict liability. MOF denied.

Olsen: We’re going to protect children of “tender years.” Legislative intent and strong policy. Age of child is immaterial. Strict liability. MOF not a defense.

Benniefield: D possessed drugs within 300 foot of a school. Court found “within 300 feet” is immaterial. D knew they were possessing drugs. MOF not a defense. Gravity.

Collazo: Mistake about the type of drug is immaterial. MOF not a defense. Gravity.

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Rape

• Consent → usually material

• Age (statutory rape) → often immaterial

Mistake of Fact - MPC

• Defense when it negates mens rea for a material element

• MPC disfavors strict liability

• MOF defeats knowingly and purpose

• MOF defeats recklessness if it shows Defendant didn’t know the risk existed

• MOF is useless for negligence since negligence is for when Defendant doesn’t know but should’ve known

Mistake of Law - Common Law

Rule #1 - The Default (Marrero): Mistake of Law is NO Defense. If you act, you are responsible for knowing the law.

• 1a. The "Definition" Exception (Regina v. Smith): Sometimes, a law requires knowledge of a specific status (e.g., "tenant" or "property of another"). If you mistake that status, you aren't ignoring the law; you are ignoring a factabout the world. ("I didn't know I was legally babysitting").

• 1b. The "Official" Override (Estoppel): Reliance on a "Highest Authority" official (Statute/Judge/AG, not a cop).

• 1c. The "Tax" Exception (Cheek): Complex statutes (Taxes) using the word "willfully." Here, the law requires you to know the duty exists.
  

Rule #2 - The Omission Exception (Lambert): We don't punish Omissions without notice.

• The Logic: You can’t be expected to read rules when you didn't "enter the game" (no positive act).

• The 3 Triggers (Must have ALL):

  1. Omission: You failed to act (Passive).

  2. Regulatory: Low stigma/minor punishment (Malum prohibitum).

  3. No Notice: No actual knowledge + no reason to suspect the duty.
     

Rule #3 - The Severity Check (Staples):

• High Penalty (Felony/Jail): We can't lock up people who didn't know the FACTS.

  • The Logic: The penalty is too high for Strict Liability. The Court "reads in" Mens Rea.

  • The Test: Did they know the nature of the item (e.g., that the gun was automatic)?

    • If YES (Knew it was a machine gun, didn't know law): Guilty.

    • If NO (Didn't know it was a machine gun): Not Guilty.

• Low Penalty (Fine): It is Strict Liability (Balint). We don’t care if you knew the facts OR the law.

Mistake of Law - MPC

Under the Model Penal Code, mistake of law is not a defense—ignorance or misunderstanding of the law ordinarily does not excuse criminal liability.

Exceptions:

1. No fair notice of the law (legality principle).

2. Reasonable reliance on official government authority.