Mistake Of Law And Mistake Of Fact
1. Mistake of Law
Definition:
A mistake of law occurs when a person is unaware that their act or omission is illegal, or misunderstands the law.
General principle: Ignorance of the law is no excuse.
In most legal systems, claiming “I didn’t know it was illegal” does not absolve you from liability.
Example:
If someone sells goods without a license thinking it is legal, they are still liable because the law applies to everyone, regardless of knowledge.
Key Case Laws:
1.1 Cheek v. United States (1991, USA)
Facts: The defendant argued that he honestly believed he was not required to pay federal taxes.
Held: The court allowed consideration of genuine misunderstanding of law only in criminal intent cases, but ignorance alone doesn’t automatically excuse the offense.
Principle: A genuine, good-faith misunderstanding of law can sometimes negate mens rea (criminal intent), but simple ignorance is not enough.
1.2 Regina v. Smith (1915, UK)
Facts: The defendant claimed he didn’t know a certain act was illegal under military law.
Held: Mistake of law is not a defense. Everyone is expected to know the law.
Principle: Legal ignorance cannot excuse criminal liability.
1.3 DPP v. Morgan (1976, UK)
Facts: Defendants claimed they believed a woman consented to sexual activity because she didn’t explicitly refuse.
Held: A mistaken belief about law (consent rules) is not usually a defense, though mistake of fact (belief about consent) can be considered.
Principle: Confirms the fine distinction between mistake of law and mistake of fact.
2. Mistake of Fact
Definition:
A mistake of fact occurs when a person acts under a false belief about a fact, not the law.
This can sometimes negate criminal intent (mens rea) if it shows the act was not done knowingly or intentionally.
Example:
Taking someone else’s umbrella thinking it’s your own may not amount to theft because there is no intention to steal.
Key Case Laws:
2.1 R v. Tolson (1889, UK)
Facts: A woman married another man believing her first husband was dead.
Held: She genuinely believed her husband was dead, so she was not guilty of bigamy.
Principle: Honest mistake of fact can negate criminal liability.
2.2 R v. Prince (1875, UK)
Facts: A man took a girl believing she was above 16, but she was underage.
Held: Conviction depends on intent and knowledge of the fact. If mistake is honest and reasonable, liability may be reduced.
Principle: Mistake of fact can sometimes be a defense if it negates mens rea.
2.3 R v. Williams (Gladstone) (1984, UK)
Facts: The defendant intervened in what he thought was an assault on a young man. In reality, the situation was misunderstood.
Held: Honest belief in facts (even if mistaken) can justify actions if the belief was genuine.
Principle: Mistake of fact can make an otherwise unlawful act lawful if it negates wrongful intent.
2.4 People v. Marrero (1977, USA)
Facts: The defendant possessed a firearm thinking he was legally allowed as a security officer.
Held: Mistake of fact about a legal right may sometimes negate mens rea if it concerns factual entitlement, not general law ignorance.
Principle: Distinguishes between mistakes about facts and mistakes about law.
Key Differences Between Mistake of Law and Mistake of Fact
| Feature | Mistake of Law | Mistake of Fact |
|---|---|---|
| Definition | Misunderstanding legal rule | Misunderstanding factual situation |
| Legal Effect | Usually not a defense | Can negate mens rea, may be a defense |
| Example | Selling alcohol without license thinking it is legal | Taking someone’s bag thinking it’s yours |
| Case Example | Regina v. Smith, Cheek v. USA | R v. Tolson, R v. Williams |
✅ Summary:
Mistake of law generally cannot excuse criminal liability.
Mistake of fact can excuse or reduce liability if it negates intent.
Courts carefully distinguish between misunderstanding legal rules vs. misunderstanding the facts.
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