Mistake of Law / Mistake of Fact

"I didn't realize that was illegal." "I didn't mean for that to happen."

When are these legal defenses to a crime?

The answer, as you will see, depends on the particular situation.

Mistakes are a common place part of the human experience. In our fast paced, information driven society, it is impossible to retain all of the information with which we are bombarded.

However, some mistakes can have grave consequences.  It is important to know what mistakes are considered excusable in the eyes of the law and what mistakes can send you to jail.

This article will discuss the California legal defenses of mistake of law and mistake of fact.

In order to help you better understand the California legal defenses of mistake of law and mistake of fact, our Los Angeles criminal defense attorneys1 will address the following:                    (click on a title to proceed directly to that section)

1. Overview of mistake of law as a
California legal defense
2. When can I use mistake of law as
a defense?
3. Overview of mistake of fact as a
California legal defense.
4. When can I use mistake of fact as a
legal defense?
5. Mistake of fact as to consent in sex cases
6. Mistake of fact s to age in statutory
rape cases

If, after reading this article, you would like more information, we invite you to contact us at Shouse Law Group.

1. Overview of mistake of  law as a
California legal defense

One of the most important principles of criminal law is that ignorance of the law is not an excuse for a crime.  This means just because a person doesn't realize that what he or she is doing is illegal, does not eliminate that person's responsibility for the corresponding crime.2

However, there are some exceptional situations where California criminal law will excuse your mistake as a result of ignorance of the law or mistaken belief that the law is something other than it is.

Generally speaking, mistake of law will not be a valid defense in a criminal case.  This is because of the general rule that when a person does something illegal, he is presumed to know the law.3

Our society expects its citizens be informed of the laws of the land.  Public policy favors holding people responsible for knowing the basic laws of their locales.

However, if you have an honest (but mistaken) belief that your conduct is lawful, there is a possibility you may be able to assert mistake of law as a legal defense.

2. When can I use mistake of law as a
legal defense?

Mistakes negating the intent or other required mental state of the crime

In order to serve as a successful California legal defense, a mistake of law must be a mistake that negates the specific intent or other mental state that is a required element of the crime.4

Each California crime consists of several elements.  In order to convict someone of a crime a prosecutor must prove each element of the crime beyond a reasonable doubt.5 An element of many crimes is that the perpetrator possess a certain mental state that accompanies his illegal conduct.6

Mistake of law serves as a defense when this mental state is negated by the honest, but mistaken belief that you are acting lawfully.  It is important to note that this belief doesn't necessarily need to be reasonable, as long as it is honest.

Let's take a look at an example...

Example: Joe has an honest belief that California's Compassionate Use Act gives him permission to open up a marijuana coop with marijuana growers and sell marijuana.

Joe begins selling marijuana without a license and is subsequently arrested. He is charged with the California crime of conspiracy and the sale of marijuana per CA Health and Safety Code § 11360.

Joe raises the defense of mistake of law because he honestly believed California Compassionate Use Act gave him permission to sell marijuana.

In this case, the crime of conspiracy requires a specific intent to violate California drug laws. To be guilty of conspiracy, Joe must have known what he was doing illegal and he must have intended to break the law.7

Because Joe honestly believed he had permission to sell marijuana under the law--and therefore did not intend to violate any drug laws--his honest mistake of law could serve as a defense to the conspiracy charge.

However, it is important to note a mistake of law defense would not help Joe with the marijuana sale charge because this charge does not require that Joe know that the sale of marijuana is illegal.  All that matters is whether he sold marijuana or not.8

3. Overview of mistake of fact as a
California legal defense

Mistake of fact is a more common (and usually a more effective) defense than mistake of law. If you act under an honest and reasonable mistake of fact, you are typically not guilty of the crime.9

Much like mistake of law, the mistake of fact defense tends to be used to disprove the criminal intent associated with a crime.10 However, unlike mistake of law, a mistake of fact must at least in some cases be reasonable in order to be a successful defense. 11

4. When can I use mistake of fact as a California legal defense?

As discussed above, the mistake of fact defense may be used to negate the criminal intent or mental state required for the crime.

Let's take a look at some examples...

Example: David lends Andy a lawnmower. Andy returns the lawnmower and then goes and buys a new one of the same model. David goes and takes the new lawnmower from Andy's garage, believing it to be the loaner. David is mistaken.

Andy accuses David of the crime of petty theft.  A mistake of fact defense for David would likely be successful in this example.  Theft requires that you intend permanently to deprive someone else of his or her personal property.12

David honestly believed the lawnmower was the one he previously lent Andy, and therefore that he had a right to reclaim it. His honest and reasonable mistake disproves any intent to permanently deprive Andy of his personal property.


Example:  David points a gun at Andy with the honest belief that it is not loaded. He pulls the trigger. David is mistaken. There is one bullet in the chamber. It fires and kills Andy.

David is charged with California First Degree Murder for Andy's death.  David raises mistake of fact as to the gun being loaded as a defense.

David again would likely be successful in raising mistake of fact because First Degree Murder requires there to be an intent to kill that is either willful or premeditated13.

David's mistake in believing the gun was not loaded disproves that he had an intent to kill Andy. Thus mistake of fact would serve as a defense to a First Degree Murder charge (however David may still be found guilty of a lesser crime such as California second degree murder or Negligent discharge of a firearm).
5.  Mistake of fact as to consent in rape cases

Mayberry Defense

Mistake of fact may also serve as a narrow defense in a rape case if an accused has a mistaken belief that the alleged victim had consented to sexual intercourse.

Stated in Penal Code 261, the California crime of rape is defined as nonconsensual intercourse accomplished by means of threats, force, or fraud.14

As discussed previously, each crime consists of elements.  The prosecution must prove each element of the crime beyond a reasonable doubt.15

The element most often at issue in rape cases is whether the accuser consented to the sex.

In People v. Mayberry the California Supreme 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 perquisite under Penal code Section 20 to a conviction of kidnapping or rape under by means of force or threat."16

An essential element of rape is that it be against the will of the victim. Therefore a reasonable mistake of fact as to whether there was consent could serve as a defense.17

Many rape cases boil down to a he said / she said with the accuser saying there was no consent and the accused saying that there was. A jury is left to decide who is telling the truth.18

A Mayberry defense of mistake of fact allows the jury to conclude that both the accuser and the accused are telling the truth, but there was simply a miscommunication.

However, the mistake must still be reasonable.  When someone relies on a Mayberry defense, that person must show some evidence of conduct by the accuser which led the accused reasonably to believe the accuser was consenting.19

Example: David goes on a date with Annie.  They go back to her apartment after the date.  Annie takes off her clothes, kisses David and asks David "Would you like to have a drink?"

David mistakenly believes he hears Annie say "Would you like to have sex?" He takes Annie and proceeds to have intercourse with her.

David's mishearing of Annie's question caused him to believe Annie wanted to have sex with him.  Annie's conduct of taking off her clothes and kissing David, could be evidence that reasonably led David to believe Annie consented to the sex.

Because David's belief was honest, reasonable, and supported by Annie's conduct, David could possibly succeed with a Mayberry defense.
6. Mistake of fact in statutory rape cases

The mistake of fact defense is often asserted in statutory rape charges.

Stated in Penal Code 261.5, California statutory rape law makes it a crime to engage in sexual intercourse with a person under 18.20

Suppose a man has sex with a 17-year-old young lady. She tells him that she's 20-years-old. She looks about 20. The man honestly and reasonably believes her to be an adult. In such a case, mistake of fact can serve as a valid legal defense to the crime.21

However it is important to note there is a strong public policy in protecting children under 14 years of age.

The California Supreme Court has ruled that even a good faith, reasonable mistake of age with respect to child under the age of 14 is not a defense.22

In other words, the mistake of fact could only serve as a defense in statutory rape cases where the minor is 14 years of age or older.23

For more information about mistake of law and mistake of fact defenses, please don't hesitate to contact us. Our California criminal defense attorneys practice throughout the state, including the San Francisco Bay area, San Jose, Alameda County, Ventura, Los Angeles, Orange County, San Bernardino, Riverside and many nearby areas.


1 Our Los Angeles criminal defense attorneys have local law offices in Beverly Hills, Burbank, Glendale, Lancaster, Long Beach, Los Angeles, Pasadena, Pomona, Torrance, Van Nuys, West Covina, and Whittier.

2 People v. McLaughlin (1952) 111 Cal.2d 781, 788 "[Defendants] labor under the delusion that if they are ignorant of a statute that proscribes the doing of an act they cannot be guilty of a crime for agreeing to do such act. No doctrine is more universal or of more ancient vintage in the law that ignorance of the law excuses no one."

3 CALJIC 4.36

4 People v. Smith (1966) 63 Cal. 2d 779.

5 Cal. Pen. Code § 1096

6 CALJIC 3.31.5

7 California Penal Code 182 PC - Conspiracy. ("(a) If two or more persons conspire: (1) To commit any crime. (2) Falsely and maliciously to indict another for any crime, or to procure another to be charged or arrested for any crime. (3) Falsely to move or maintain any suit, action, or proceeding. (4) To cheat and defraud any person of any property, by any means which are in themselves criminal, or to obtain money or property by false pretenses or by false promises with fraudulent intent not to perform those promises. (5) To commit any act injurious to the public health, to public morals, or to pervert or obstruct justice, or the due administration of the laws. (6) To commit any crime against the person of the President or Vice President of the United States, the Governor of any state or territory, any United States justice or judge, or the secretary of any of the executive departments of the United States. They are punishable as follows: When they conspire to commit any crime against the person of any official specified in paragraph (6), they are guilty of a felony and are punishable by imprisonment in the state prison for five, seven, or nine years. When they conspire to commit any other felony, they shall be punishable in the same manner and to the same extent as is provided for the punishment of that felony. If the felony is one for which different punishments are prescribed for different degrees, the jury or court which finds the defendant guilty thereof shall determine the degree of the felony the defendant conspired to commit. If the degree is not so determined, the punishment for conspiracy to commit the felony shall be that prescribed for the lesser degree, except in the case of conspiracy to commit murder, in which case the punishment shall be that prescribed for murder in the first degree. If the felony is conspiracy to commit two or more felonies which have different punishments and the commission of those felonies constitute but one offense of conspiracy, the penalty shall be that prescribed for the felony which has the greater maximum term. When they conspire to do an act described in paragraph (4), they shall be punishable by imprisonment in the state prison, or by imprisonment in the county jail for not more than one year, or by a fine not exceeding ten thousand dollars ($10,000), or by both that imprisonment and fine. When they conspire to do any of the other acts described in this section, they shall be punishable by imprisonment in the county jail for not more than one year, or in the state prison, or by a fine not exceeding ten thousand dollars ($10,000), or by both that imprisonment and fine. When they receive a felony conviction for conspiring to commit identity theft, as defined in Section 530.5, the court may impose a fine of up to twenty-five thousand dollars ($25,000). All cases of conspiracy may be prosecuted and tried in the superior court of any county in which any overt act tending to effect the conspiracy shall be done. (b) Upon a trial for conspiracy, in a case where an overt act is necessary to constitute the offense, the defendant cannot be convicted unless one or more overt acts are expressly alleged in the indictment or information, nor unless one of the acts alleged is proved; but other overt acts not alleged may be given in evidence.")

8 People v. Urziceanu (2005) 132 Cal.4th 747, 779 - [defendant's good faith belief that Compassionate Use Act permitted him to form cooperative to provide marijuana entitled him to mistake of law defense to negate specific intent required for conspiracy conviction]

9 CALJIC 4.35 -- Ignorance or mistake of fact as a California legal defense. ("An act committed or an omission made in ignorance or by reason of a mistake of fact which disproves any criminal intent is not a crime. Thus a person is not guilty of a crime if [he] [she] commits an act or omits to act under an actual [and reasonable] belief in the existence of certain facts and circumstances which, if true, would make the act or omission lawful.")

10 See Same.

11 See same.

12 Cal. Penal Code § 484 and 488

13 Cal. Penal Code 187 (a), malice may be express or implied.                    Express malice means that you specifically intend to kill the victim. Malice is implied when: (a) The killing resulted from an intentional act; (b) The natural consequences of the act are dangerous to human life; and (c) The act was deliberately performed with knowledge of the danger to, and with conscious disregard for, human life.4Both first- and second-degree murder require malice.

14 California Penal Code 261 -- Rape defined. ("(a) Rape is an act of sexual intercourse accomplished with a person not the spouse of the perpetrator, under any of the following circumstances: (1) Where a person is incapable, because of a mental disorder or developmental or physical disability, of giving legal consent, and this is known or reasonably should be known to the person committing the act. Notwithstanding the existence of a conservatorship pursuant to the provisions of the Lanterman-Petris-Short Act (Part 1 (commencing with Section 5000) of Division 5 of the Welfare and Institutions Code), the prosecuting attorney shall prove, as an element of the crime, that a mental disorder or developmental or physical disability rendered the alleged victim incapable of giving consent. (2) Where it is accomplished against a person's will by means of force, violence, duress, menace, or fear of immediate and unlawful bodily injury on the person or another [rape will be charged]. (3) Where a person is prevented from resisting by any intoxicating or anesthetic substance, or any controlled substance, and this condition was known, or reasonably should have been known by the accused. (4) Where a person is at the time unconscious of the nature of the act, and this is known to the accused. As used in this paragraph, "unconscious of the nature of the act" means incapable of resisting because the victim meets one of the following conditions: (A) Was unconscious or asleep. (B) Was not aware, knowing, perceiving, or cognizant that the act occurred. (C) Was not aware, knowing, perceiving, or cognizant of the essential characteristics of the act due to the perpetrator's fraud in fact. (D) Was not aware, knowing, perceiving, or cognizant of the essential characteristics of the act due to the perpetrator's fraudulent representation that the sexual penetration served a professional purpose when it served no professional purpose. (5) Where a person submits under the belief that the person committing the act is the victim's spouse, and this belief is induced by any artifice, pretense, or concealment practiced by the accused, with intent to induce the belief. (6) [Penal Code 261 PC California rape will be charged] Where the act is accomplished against the victim's will by threatening to retaliate in the future against the victim or any other person, and there is a reasonable possibility that the perpetrator will execute the threat. As used in this paragraph, "threatening to retaliate" means a threat to kidnap or falsely imprison, or to inflict extreme pain, serious bodily injury, or death. (7) Where the act is accomplished against the victim's will by threatening to use the authority of a public official to incarcerate, arrest, or deport the victim or another, and the victim has a reasonable belief that the perpetrator is a public official. As used in this paragraph, "public official" means a person employed by a governmental agency who has the authority, as part of that position, to incarcerate, arrest, or deport another. The perpetrator does not actually have to be a public official. (b) As used in this section [for California rape], "duress" means a direct or implied threat of force, violence, danger, or retribution sufficient to coerce a reasonable person of ordinary susceptibilities to perform an act which otherwise would not have been performed, or acquiesce in an act to which one otherwise would not have submitted. The total circumstances, including the age of the victim, and his or her relationship to the defendant, are factors to consider in appraising the existence of duress. (c) As used in this section, "menace" means any threat, declaration, or act which shows an intention to inflict an injury upon another."

15 Cal. Pen. Code § 1096

16 People v. Mayberry (1975) Cal.3d 143, 153.

17 CALJIC 10.00. Rape-Spouse and Non-Spouse-Force or Threats. ("In order to prove this crime, each of the following elements must be proved: [1] A male and female engaged in an act of sexual intercourse; [2] The two persons were [not] married to each other at the time of the act of sexual intercourse; [3] The act of intercourse was against the will of the alleged victim; [4] The act was accomplished by means of force, violence, duress, menace, or fear of immediate and unlawful bodily injury [to the alleged victim] [or] [to another person].")

18 People v. Romero (1985) 171 Cal.3d 1149, 1155.

19 Same as above.

20 California Penal Code 261.5 -- Unlawful sexual intercourse with person under 18; age of perpetrator; civil penalties. ("(a) Unlawful sexual intercourse is an act of sexual intercourse accomplished with a person who is not the spouse of the perpetrator, if the person is a minor. For the purposes of this section, a "minor" is a person under the age of 18 years and an "adult" is a person who is at least 18 years of age.")

21People v. Hernandez (1964) 61 C.2d 529, 534-35 (defendant was convicted of statutory rape of a minor 17 years and 9 months old, who voluntarily consented to the act. The trial judge rejected an offer of proof that defendant reasonably and in good faith believed she was 18. Reversed on appeal.

22People v. Olsen (1984) 36 C.3d 638, 645-646 [reasonable mistake of age is not a defense to a charge of lewd or lascivious conduct with a child under the age of 14 years].

23 Same as above.

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