Criminal Case Defense: The Difference Between Mistake of Fact and Mistake Of Law


During criminal cases, the defendant might claim that the crime committed was, in fact, the result of an honest mistake rather than an intentional act. 

Mistake of fact and mistake of law are legal defenses that defendants can invoke during a trial. These defenses are used depending on the crime’s circumstances or a misunderstanding of the law.

During a mistake of fact defense, the accused proves that they did not intentionally commit a crime but did so because they misunderstood a particular fact. An example of a mistake of fact defense is when the defendant believes they had the right to property during theft charges.

The mistake of law defense, on the other hand, shows that the accused did not have the mental state to commit the crime due to a misunderstanding of the law.  For instance, a defendant may claim that they believed the law provided the legal right to do the accused act. In robbery cases, the accused might state that they were trying to retrieve their property and did not intend to break the law. 

Read on to understand these defenses, their use, and situations when they do not apply. 

What Is the Mistake of Law Defense?

We can break down the mistake of law defense into two parts; the lack of intent or mental state for a crime and misunderstanding or ignorance of the law. This type of defense may be challenging to establish due to existing principles such as “ignorance of the law is not an excuse for a crime,” meaning individuals have the sole responsibility to be aware of existing laws. 

Mistake of law can be applied in the following circumstances:

  • When the defendant was acting based on a judicial decision that the system later overruled
  • When the law has not been published
  • When the defendant’s actions were a result of an interpretation from an applicable official
  • When the defendant’s actions relied upon a law or statute that was later deemed unconstitutional

When referring to reliance on any of the mentioned sources, the defendant must be reasonable. It would be impractical to claim that the mistake was based on a law from 200 years ago when it is clear that these laws have undergone tremendous changes over time.

Also, applicable officials in this context are limited to judges or federal or state agencies. Any reliance on a party, such as a private attorney, will not qualify as a mistake of law. For this defense to be effective, the mistake of law has to be proved as honest and made in good faith. 

What Is the Mistake of Fact Defense?

Like the mistake of law, the mistake of fact defense also involves proving that the accused did not have intent because they misunderstood a particular fact. This very misunderstanding, therefore, negates an element of the charged crime. The defense will work if the mistake is honest and reasonable. 

For example, a person accused of larceny may prove their actions were a mistake if they believe the property they acquired was rightfully theirs. However, if the individual was warned that they had no rights over the property, they cannot claim that they mistakenly acquired the property. The mistake has to appear reasonable to the judge or jury. 

Mistake and Strict Liability Crimes

It is crucial to note that these two defenses will not work in strict liability crimes. Examples of strict liability crimes are sex with a minor, selling alcohol to a minor, drunk driving, and driving over the speed limit. In cases involving minors, the “mistake” defense is not applicable even when the children could easily be mistaken to be of age. 

In strict liability cases, the prosecutor must prove that the accused committed a crime, thereby violating the law. The mental state or intent of the accused is insignificant in such a case. Since the mistake defenses rely on intent, they are irrelevant in strict liability cases.


Defendants can use the mistake of law and fact defenses to prove they committed an alleged crime without intent due to a lack of proper knowledge of the laws. While they may work, ignorance of the law is rarely a strong defense. Additionally, these defenses cannot be used in strict liability cases, as their grounds are irrelevant. 

Always hire a criminal defense lawyer if you are facing criminal charges. They will help you determine your best defense strategy based on the case. 

Share this


Chang Beer: Thailand’s Beloved Brew

Known for its unique blend and global acclaim, discover what makes Chang Beer Thailand's beloved brew since 1995.

Kozel: The Czech Republic’s Smooth and Flavorful Beer

Mix your ideal blend with Kozel, the Czech Republic's smooth and flavorful beer, and discover a new world of taste.

What Is the Difference Between Beer and Ale?

When exploring different types of beer, you might wonder what makes an ale unique. The difference lies in the yeast used and the brewing temperatures. Ales use top-fermenting yeast and are brewed at warmer temperatures, giving them a fruity and complex flavor. On the other hand, lagers use bottom-fermenting yeast and are brewed at cooler temperatures, resulting in a...

Recent articles

More like this