“I Made a Mistake” Can be a Winning Defense

Everybody makes mistakes. This is what we tell our children the minute they are old enough to understand, and we also tell them not to cry over spilled milk. When we say this, it means that we understand mistakes happen, and will not hold someone responsible for honest errors. The good news is that this can also be true for adults. If you have been accused of committing a crime, and you truly made a mistake, then in some instances, you might have a successful defense.

Mistakes of Fact and Mistakes of Law

There are two types of mistakes that an experienced criminal defense attorney should explore when building a defense on behalf of a client; mistakes of fact and mistakes of law. 

Mistake of Fact

While a mistake of fact is sometimes a defense to a crime, the general rule is that ignorance is not an excuse. There are some exceptional situations, however, where a mistake can be excused under the law. A mistake of fact is when a person acts upon a mistaken belief, and their actions result in a violation of law. Here is an example: imagine if you leave a crowded party, and you pick up the nearest iPhone, because it looks just like yours, and put it in your purse. When you leave, you realize you have the wrong telephone, but you do not realize it until the police pull you over and arrest you for having stolen property.  In this instance, mistake of fact would be an appropriate defense, because you acted under the misunderstanding that you were taking your own telephone.

California specifically allows the affirmative defense of Mistake of Fact against all crimes requiring specific intent. California Criminal Jury Instruction 3406 instructs a jury that if the defendant’s conduct would have been legal under the facts he or she believed to be true at the time, then he or she is not guilty of the crime. Put another way, you are not guilty of a crime if you did not have the mental state required to commit the crime, because you mistakenly believed or did not know a fact.      

Mistake of Law

Like with mistakes of fact, the general rule is that people are expected to be aware of the law wherever they are in the United States. However, just like mistake of fact cases, asserting the defense of mistake of law can succeed if the mistake nullifies the intent or other mental state that is required as an element of the crime. Every California crime has several elements, each of which must be proven beyond a reasonable doubt. One element of most crimes is that the accused must possess a certain mental state when committing the crime, and this can be negated when a defendant successfully asserts that he or she was acting on a belief that his or her actions were honest, lawful actions. The belief does not have to be reasonable; just honest.

This is a more difficult defense to bring than mistake of fact, since the general public is expected to know the law. In situations where a law has not yet been passed, however, or if you relied on a law that has since been overturned or found to be unconstitutional, or if you relied on an official legal interpretation of a law that was later found to be incorrect, then this defense can be advanced. Reliance on such a mistake must be reasonable.

What does this mean? You cannot rely on something that is 100 years old, or something that a reasonable person would understand is a mistake. You can tell how difficult it is to prevail on a mistake of law defense by California Criminal Jury Instruction 3407, which instructs a jury that it is not a defense to the crime being charged that the defendant was unaware he or she was breaking the law, or that he or she believed the act was lawful.


Mistakes of fact are far more common than mistakes of law, and legally far more effective. If you act under an honest and reasonable mistake of the facts, in almost all cases you will not be guilty of the crime you are charged with. An important exception to this is when it comes to cases of statutory rape of a child under the age of 14. Even if you can make a case that you reasonably and honestly believed the alleged victim was the age of consent, the defense is not allowed at all if the victim was under the age of 14. Other than that, however, in general if you can show a reasonable and honest mistake, then criminal liability based on a mistake of fact can likely be avoided.

Relying on a mistake of law is far riskier, and there are very few circumstances under which it can be successfully advanced. Because of the mixed legal authority surrounding medicinal marijuana (and marijuana sales generally), and the dichotomy between federal and state law, it is conceivable that a mistake of law defense could be successful if someone was arrested for selling marijuana in a manner that complied with state laws but not federal laws.

If you are facing criminal charges based on what you believe is an honest mistake, do not hesitate to call Ozols Law Firm. It is important to have an experienced San Diego criminal defense lawyer on your side. Mr. Ozols will review your case and advise you whether or not you have a successful defense based on mistake of law, mistake of fact, or any other affirmative defense that can help mitigate or eliminate criminal liability.