“Mistake of fact” and “mistake of law” are both legal defenses that a defendant may invoke to challenge certain criminal charges. These defenses are based on the theory that the accused acted based on an honest mistake, and thus lacked the mental state or “mens rea” that the crime, by defintion, requires.
In a mistake of fact defense, an accused asserts that he/she did not have the intent to commit a crime because he or she misunderstood a particular fact. For example, defendants can use the defense to challenge theft charges by showing that they made a mistake and reasonably believed that they had a right to the property they took. The defense is only valid, however, if the mistake is honest and reasonable.
Under a mistake of law defense, a defendant shows that he/she did not have the mental state to commit a crime because of a misunderstanding of the law. An example is a defendant saying that he did not conspire to commit a crime because he/she believed a law provided the legal right to do the conspired act. This misunderstanding, though, has to be made in good faith for the defense to work.
Note that these two defenses do not apply to strict liability cases. This is because a defendant’s intent is irrelevant here. A prosecutor only has to prove that a defendant performed some illegal act (such as having sex with a minor who is below the age of consent).
Our criminal defense attorneys will highlight the following in this article:
- 1. What is the mistake of fact defense?
- 2. What is the mistake of law defense?
- 3. Do these defenses apply to strict liability crimes?
- 4. What is the law in California?
1. What is the mistake of fact defense?
“Mistake of fact” refers to a legal defense where an accused shows that:
- he/she did not have the intent to commit an offense, and that
- this is true because he/she misunderstood a particular fact.1
This defense only works, though, if the defendant’s mistake is both:
- honest, and
Example: Dave and Andy are neighbors. Dave lends Andy his lawnmower. Andy cuts his grass and then returns the mower to Dave’s garage. Dave does not know that he returned it. Andy goes out and buys a new mower that is the same model of the one he borrowed.
Dave wants to cut his grass. He goes over to Andy’s home and sees the new mower parked in front of Andy’s garage. Although the mower is not his, it looks identical to it, so he takes it.
Note that with theft crimes, a defendant is only guilty if he took something with the intent to permanently deprive the owner of it.
Here, Dave can challenge any theft charge with a mistake of fact defense. While he did take Andy’s new mower, he only did so because he mistakenly thought that it was his. The mistake was reasonable since the two mowers were the same exact model. The mistake works as a defense to avoid guilt.
Note that mistake of fact may serve as a narrow defense in rape cases. Two elements that a prosecutor must prove to successfully convict a person of rape are:
- the defendant had sexual intercourse with another person, and
- the other person did not consent to the intercourse.
A defense, then, is that the accused had a reasonable mistake that the “victim” consented to sex.
Example: Joe goes on a date with Lisa. After dinner, she asks him back to her place. Once inside her apartment, Lisa goes to change. She comes out of her bedroom wearing lingerie. She kisses Joe, rubs his shoulder, and asks him if he wants a drink.
Taking all of this in, Joe believes that Lisa wants to have sex. He proceeds to take her back in her bedroom and has sexual intercourse with her. Joe is later charged with rape.
Here, Joe may be able to use mistake of fact as a defense to contest the charge. The facts tend to support the idea that Joe had a reasonable belief, although a mistaken one, that Lisa was consenting to have intercourse. These include the facts that:
- Lisa asked Joe back to her place,
- she changed out of her clothes and into lingerie, and
- she kissed Joe and rubbed his shoulder.
2. What is the mistake of law defense?
“Mistake of law” refers to a legal defense that says an accused:
- did not have the intent, or mental state, to commit a crime, and
- this is true because he/she misunderstood the law.3
Note that this defense is often difficult to establish. This is because it is a well-founded principle that ignorance of the law is not an excuse for a crime.
Nevertheless, the defense still applies in some cases. To be effective, the misunderstanding or mistake of law has to be:
- honest, and
- made in good faith.4
Example: Jack has an honest belief that a state statute gives him permission to: (1) open a marijuana co-op with other marijuana growers; and, (2) sell marijuana – all without any type of license.
Jack begins selling marijuana and is soon arrested. He is charged with conspiracy and the unlawful sale of marijuana.
Note that an accused is guilty of conspiracy only if he/she had a specific intent to violate a law.
Here, a mistake of law defense might help Jack successfully challenge the conspiracy charge. Jack honestly believed that he had permission to sell marijuana under the law. Therefore, he did not intend to violate any drug law and did not have the requisite mental state to “conspire.” He simply made a mistake, in good faith, as to the interpretation of a state statute.
It is important to note, though, that the defense would not challenge the unlawful sale of marijuana charge. This is because the crime does not require any showing of unlawful intent. A prosecutor just has to show that a defendant sold the drug without a license to do so.
3. Do these defenses apply to strict liability crimes?
The mistake of fact and mistake of law defenses do not apply in strict liability cases.5
Strict liability crimes are offenses where, to get a conviction, a prosecutor only has to prove that:
- the accused committed a certain act, and
- that act violated the law.
The prosecutor does not have to show that the accused acted with any:
- wrongful intent, or
- specific mental state.
Recall that the above defenses work as legal defenses solely because they negate criminal intent. Since strict liability crimes do not care about intent, the defenses are not effective with these offenses.
Consider, for example, a DUI charge for driving with a BAC of 0.08% or higher. This is a strict liability crime. A person is guilty so long as his or her BAC was 0.08% or higher. The above defenses do not work because the driver’s mental state is irrelevant.
4. What is the law in California?
California law recognizes mistake of fact as a defense when it negates the requisite mental state necessary for the crime. Specifically, jury instruction CALCRIM 3406 states that “the defendant is not guilty (of the crime) if he/she did not have the intent or mental state required to commit the crime because he/she [reasonably] did not know a fact or [reasonably and] mistakenly believed a fact.”
Note that when the defense is used in rape cases, it is known as a “Mayberry defense.” This is because a California court authorized the defense in rape cases in People v. Mayberry. In that case, the court said:
“If a defendant entertains a reasonable and bona fide belief that a [person] voluntarily consented to accompany him and engage in sexual intercourse it is apparent he does not possess the wrongful intent that is a prerequisite…to a conviction of…rape by means of force or threat.” 6 7
California law also says a defendant can use the defense of mistake of law.8 To work, however, the mistake has to be:
- honest, or
- made in good faith.9
For additional help…
For additional guidance or to discuss your case with a criminal defense attorney, we invite you to contact us at Shouse Law Group.
- United States v. Martin, 753 F.3d 485 (2014).
- See same.
- United States v. Washington, 887 F.Supp, 2d 1077 (2012). See also United States v. Ricard, 922 F.3d 639 (2019).
- See same.
- See, for example, People v. Vogel (1956) 46 Cal. 2d 798.
- CALCRIM No. 3406 – Mistake of Fact. Judicial Council of California Criminal Jury Instructions (2017 edition).
- People v. Mayberry (1975) 15 Cal.3d 144.
- CALCRIM No. 3411 – Mistake of Law as a Defense. Judicial Council of California Criminal Jury Instructions (2017 edition).
- People v. Vineberg (1981) 125 Cal.App.3d 127. See also People v. Cole (2007) 156 Cal.App.4th 452; People v. Flora (1991) 228 Cal.App.3d 662; and, People v. Stewart (1976) 16 Cal.3d 133.