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Occasionally, a defendant’s mistake negates the criminal intent required for an offense. Mistakes can be a mistake of law or a mistake of fact. Mistake of law and fact defenses can be statutory or common law, perfect or imperfect, depending on the jurisdiction.
Mistake of Law
The basis of the mistake of law defense is that the defendant believes his or her criminal conduct is legal. The defense could be a failure of proof defense or an affirmative defense of excuse, depending on the jurisdiction (Tex. Penal Code, 2010). The Model Penal Code provides, “Ignorance or mistake as to a matter of fact or law is a defense if: (a) the ignorance or mistake negatives the purpose, knowledge, belief, recklessness or negligence required to establish a material element of the offense; or (b) the law provides that the state of mind established by such ignorance or mistake constitutes a defense” (Model Penal Code § 2.04(1)).
Most states require that the mistake of law be founded on a statute or judicial decision that is later overturned (La. Rev. Stat. Ann, 2010). The Model Penal Code states, “A belief that conduct does not legally constitute an offense is a defense to a prosecution for that offense based upon such conduct when…the actor…acts in reasonable reliance upon an official statement of the law, afterward determined to be invalid…contained in…a statute or…judicial decision” (Model Penal Code § 2.04(3) (b)).
Incorrect advice from a licensed attorney cannot form the basis of a mistake of law defense (Hopkins v. State, 2010). Nor can mistake of law be rooted in ignorance of the law because all individuals are required to know the criminal laws effective in their jurisdiction. The Model Penal Code provides, “A belief that conduct does not legally constitute an offense is a defense to a prosecution for that offense based upon such conduct when: the statute or other enactment defining the offense is not known to the actor and has not been published or otherwise made available prior to the conduct” (Model Penal Code § 2.04(3) (a)).
Example of the Mistake of Law Defense
Shelby, an attorney, researches current case law and determines that it is legal to sell products over the Internet and not charge sales tax. Shelby starts selling designer clothing on eBay and does not charge her customers any sales tax. The case decision that Shelby relied on is overturned by a court of appeals. Shelby can probably assert mistake of law as a defense to the crime of evading payment of sales tax.
Example of a Case That Is Inappropriate for the Mistake of Law Defense
Review the mistake of law defense example given in “Example of the Mistake of Law Defense”. Assume that in Shelby’s state, it is currently illegal to sell products over the Internet without charging sales tax.
Jonathan meets with Shelby, and asks her to research whether he needs to charge sales tax when he sells products over the Internet. Shelby agrees to research the matter and get back to Jonathan the next day with an answer. After Jonathan leaves, Shelby is contacted by her friend Margaret, who wants to take an impromptu trip to New York City. Margaret asks Shelby if she would like to come along. Shelby agrees, rushes home, packs for the trip, and leaves with Margaret. The next day while Shelby is watching a Broadway play with Margaret, Jonathan calls Shelby on her cell phone and asks Shelby what her research revealed about the sales tax question. Even though she has not done any research on the matter, Shelby responds, “I just finished the research. You do not need to charges sales tax when you sell products over the Internet.” If Jonathan thereafter relies on Shelby’s incorrect advice, and sells products over the Internet without charging sales tax, he probably will not be able to assert mistake of law as a defense. Incorrect advice from an attorney cannot excuse criminal conduct, even if the crime is committed because of the faulty legal opinion. Therefore, Jonathan could be charged with tax evasion in this situation.
Mistake of Fact
Mistake of fact is more likely to provide a defense than mistake of law. If the facts as the defendant believes them to be negate the requisite intent for the crime at issue, the defendant can assert mistake of fact as a defense (N.H. Rev. Stat. Ann., 2010). Mistake of fact is generally not a defense to strict liability crimes because intent is not an element of a strict liability offense (People v. Olsen, 2010).
Example of the Mistake of Fact Defense
Mickie sees Rachel, his neighbor, riding his bicycle in her driveway. Mickie walks quickly up to Rachel and demands that she get off the bike and return it to his garage. Frightened, Rachel hops off and runs to her house, leaving the bike behind. Mickie walks the bike over to his garage. Once Mickie reaches the garage, he sees that his bike, which is an exact replica of Rachel’s, is already inside. Mickie may be able to use mistake of fact as a defense to theft. As is discussed in Chapter 11 “Crimes against Property”, the intent for theft is the intent to take the property of another person. Mickie believed Rachel’s bike was his. Thus Mickie’s mistake of fact negates the intent required for this offense.
Example of a Case That Is Inappropriate for the Mistake of Fact Defense
Tina is pulled over for speeding. Tina claims her speedometer is broken, so she was mistaken as to her speed. Tina probably cannot assert mistake of fact as a defense in this case. Speeding is generally a strict liability offense. Thus Tina’s mistaken belief as to the facts is not relevant because there is no intent required for this crime.
This page titled 5.8.3: Ignorance and Mistake was last modified on Tue, 01 Sep 2026 14:18:42 GMT and is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by Mark C Fields and Carmyn A. Radetic-Fields.
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