Mistake Of Fact As A Defense To Criminal Charges

Mistake of fact, can act as a defense in a criminal case if your actions would not have been unlawful had the facts that you assumed were true. Also, your belief must be have been an honest and reasonable one or that an ordinary person would accept as reasonable.

For instance, you took the wrong briefcase or piece of luggage that was identical to your own. If you realized your mistake and tried to return it or locate the real owner, you had no intent to permanently deprive the owner of his property.

A defendant must present evidence to support the defense and to raise a reasonable doubt as to the element of intent, although this is not an affirmative defense.

An affirmative defense means that you have the burden of proving the defense by a preponderance of the evidence.

If there is credible evidence that you had a reasonable belief as to a certain set of facts that were not true but that you reasonably relied on them commit the act, then the court has a sua sponte obligation to so instruct the jury in most but not all cases.

Specific Intent Vs. General Intent Crimes

Most crimes only require general intent, meaning that you intended to perform the unlawful act or the general result of your actions rather than the specific results. For example, if you intended to touch someone in an offensive manner such as by pushing them or grabbing their genitals, then you are guilty of battery under penal code 242 pc. If the person you touched falls backwards and hits her head and dies, or the grabbing of the person’s genitals causes him to suffer a heart attack, you did not specifically intend that result. The consequence is that you could be convicted only of a lesser charge rather than first degree murder.

Mistake of fact can be a defense to a specific intent crime by negating the mens rea, or criminal intent1.


It is a crime to trespass under penal code 602 pc and take away the property of another person with intent to steal. If you thought the property was abandoned, then it is your belief that counts, not that you should have known the property was not abandoned. It may be irrelevant that your belief was unreasonable; it only focuses on whether this casts doubt on your mental state. If you had an unreasonable belief, it may exonerate you or lead to charging or convicting you of a lesser crime.

For general intent crimes, your belief in the assumed facts must have been reasonable. Examples of general intent crimes include rape under pc 261, kidnapping, battery and assault. If you had an honest and reasonable belief that the person you had sex with consented to it, or that the child you are accused of kidnapping – pc 207 was supposed to be with you and not the other parent, then you may have a defense.

When Mistake of Fact is Applicable

Mistake of fact as a defense commonly arises in rape cases, however it is not applicable in many statutory rape cases.

Mistake of fact may be used in murder cases. An example is a defendant who shot and killed another person but who claims that he did not know the gun was loaded. If the parties were not quarreling but merely examining the firearm, then the death was accidental. However, the facts may be such that the defendant may face criminal negligence charges. So long as you lacked criminal intent, were not criminally negligent and acting lawfully at the time, then your mistaken belief that the gun was unloaded may be raised and the jury so instructed.


Mistake of fact is often raised in rape cases where one party claims that the other gave consent. In California, this is referred to as a Mayberry Defense2. Again, to avail yourself of this defense, you would have had to possess a bona fide and reasonable belief that the other party voluntarily consented to sexual relations with you. This requires that the consenting party acted in such a way as to convey consent. For instance, a woman you were with accompanied you to your apartment, allowed you undress her, there was heavy fondling and discussion of sex. Consequently, you could have formed a reasonable belief that when you began to have intercourse with the woman, she had consented even if she did not specifically agree to it.

However, the woman has the right to change her mind. If she clearly tells you to stop and withdraws her consent, you must cease. This defense is also not applicable to situations where the woman was unconscious when the defendant had sex with her. If the woman consented or appeared to consent before passing out or becoming unconscious, the courts have ruled that the defendant cannot reasonably assume that her consent was ongoing.

Statutory Rape & Strict Liability Crimes

It is unlawful to have sexual intercourse with a woman under the age of 18. In some states, this is a strict liability crime under any circumstances so that your honest and reasonable belief that the woman was at least 18 is irrelevant. If she was under 18, your having had sex with her is unlawful regardless of her consent, her assurances to you that she is 18, her demeanor and maturity or any other factors.

California is distinct from those states in that strict liability in this context only applies to women under the age of 14. If the girl is at least 14, then you may assert mistake of fact but your belief must be one where a person of ordinary intelligence would agree that the woman appeared to be at least 18 based on her demeanor, appearance and her assurances to you that she was 18. If you met her in a bar and she was drinking, you might claim a reasonable belief she was 21.

California law does not recognize mistake of age as a defense in cases of lewd conduct with a minor under the age of 14, or even attempted lewd conduct with a minor under the age of 16.3.

Other strict liability crimes where mistake of fact may not be available are speeding and selling alcohol to a minor. If your speedometer was broken and you were under the mistaken impression you were traveling at the speed limit, mistake of fact is not a defense. If you sell alcohol to a minor, it is irrelevant if you honestly believed the person was 21. However, a jury could exonerate you if you reasonably relied on an ID card that looked bona fide or genuine.

Mental Illness or Intoxication

Although mental illness and intoxication may be instances of diminished capacity, these conditions are not applicable to the defense of mistake of fact. You may not use the ordinary person standard in these circumstances to excuse criminal conduct in most instances. With mental illness or diminished mental capacity, however, you can raise the insanity defense if you can prove its elements.

Intoxication does not justify a mistake of fact if an ordinary person, who is not intoxicated, would not accept the mistake as reasonable. This is irrelevant in general intent crimes like DUI where the prosecution need only prove that you were driving with a BAC of 0.08% or that you were impaired, regardless if you intended to drive impaired or have a BAC over the legal limit or had a mistaken belief that you were sober. You can still challenge the results of your BAC or the officer’s conclusion that you were under the influence while driving – VC 23152(a).

Frequently Asked Questions About The Accident Legal Defense

Question: My brother was just released from jail and was told by his lawyer that his parole officer had already registered him as a sex offender. Can he use mistake of fact as a defense?

Response: This is actually either ignorance or mistake of law rather than mistake of fact since the law requires that you personally register. You cannot rely on a lawyer’s erroneous advice to escape responsibility. Also, your brother was likely advised when he was released from prison of his obligation to register. If the court was supposed to send him a notice that he was to register personally and it did not or the court record is silent on this, then he may have a defense. Otherwise, mistake of law in this case is not a defense.

Question: I was arrested and charged with bigamy but I thought the divorce of my previous wife had been granted 6-months earlier.

Response: You can assert mistake of fact as a defense depending on the circumstances. Why did you think the divorce was finalized? Did you make any inquiries or receive any kind of notice from the divorce court? If you just assumed you were divorced without more, then your mistake may not be considered reasonable.

Question: If a person tries to rob someone with a firearm that he did not know was incapable of being fired, can he still be charged with robbery? Isn’t this a mistake of fact?

Response: This is an example of factual impossibility and it does not relieve that person of being charged with or convicted of robbery or even attempted murder if he tried to shoot the person regardless if the firearm was disabled.

Question: What is the difference between mistake of fact and mistake of law?

Response: As described above, mistake of fact is a reasonable reliance on an assumed set of facts that are erroneous. Mistake of law is rarely a viable defense. For instance, California recently approved a referendum legalizing small amounts of recreational marijuana but it does not go into effect until 2018. If you now light up a joint in a public area and are arrested, you cannot assert that you honestly believed that it was legal or that you could even smoke marijuana in public.

Mistake of law can be a defense if you had a duty to act pursuant to reporting requirements but neglected to do so but your neglect was because of your ignorance and was not willful. This might apply to failing to adhere to reporting requirements for IRS purposes or as a sex offender if certain circumstances are present.

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  1. The mens rea requirement is premised upon the idea that one must possess a guilty state of mind and be aware of his or her misconduct; however, a defendant need not know that their conduct is illegal to be guilty of a crime. Rather, the defendant must be conscious of the “facts that make his conduct fit the definition of the offense.”, available at https://www.law.cornell.edu/wex/mens_rea []
  2. People v. Mayberry (1975) Cal.3d 14, available at https://scocal.stanford.edu/opinion/people-v-mayberry-23014 []
  3. People v. Paz (2000) 80 Cal. App. 4th 293, 294, available at https://law.justia.com/cases/california/court-of-appeal/4th/80/293.html []