Mistake of Fact (Definition And Legal Defense: Overview)

What is Mistake of Fact?

How do you legally define it?

How does it work in criminal and contract law?

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What Is Mistake of Fact

A “mistake of fact” is when a person reasonably or honestly makes a mistake on an important fact leading him or her to act in a prejudicial way or commit a crime.

In criminal law, a person can make a sincere mistake of fact resulting in the commission of a criminal offense.

For example, a person who owns a dog of a specific breed and goes to an event where other dog owners showcased their dogs.

By mistake, a dog owner returns home with a dog that appeared to be her dog but in reality it was not.

This is a good example of a mistake of fact and not theft.

If that were the case, the ‘mistake of fact’ defense can be raised to attack the element of “intent” required to be convicted of a crime.

In contract law, a similar mistake on factual aspects of the contract can result in a person signing a prejudicial contract.

If the plaintiff is able to demonstrate that there was a genuine or reasonable mistake in factual circumstances surrounding the formation of the contract or other, the court may rescind the contract or provide other remedies.

Mistake of Fact Definition

According to Cornell Law School’s Legal Information Institute, the mistake of fact is defined as follows:

A mistake of fact can happen in many situations, such as:

• Mistake of fact criminal law
• Mistake of fact contract law 

In criminal law, a mistake of fact can be used as a defense to attack the element of intent required to prove that a crime was committed.

In contract law, a mistake of fact can be used as an argument by a plaintiff who made a mistake on the terms of a contract.

Mistake of Fact Defense

In criminal cases, the mistake of fact defense can be used to demonstrate that the defendant did not have the intention to commit a crime. 

Essentially, the defendant’s argument is that he or she made a mistake relating to the circumstances of the crime in such a way that negates one of the elements of the crime.

The defendant must demonstrate that:

• He or she did not have the intention of committing an offense 
• There was a misunderstanding about a certain fact (where the mistake was honest and reasonable) 

When the defendant is able to successfully establish a defense on genuine mistake relating to facts, the prosecutor’s ability to prove the commission of a crime beyond a reasonable doubt will be challenged.

The mistake of fact defense can apply to many crimes but not all.

For example, when a person commits a strict liability offense, the person would not be able to use the factual mistake argument as a valid defense.

The reason for that is that strict liability offenses do not consider the element of intention for the crime to be proven by the prosecutor.

If a company or person is not authorized to sell alcohol to a minor, even a reasonable and honest belief that the person was of legal age would not suffice as a defense.

Mistake of Fact Example

To better understand the concept, let’s look at a few examples of factual mistakes that can happen.

One good mistake of fact example is in criminal law where a person accused of larceny argues that subjectively he or she believed owning the property he or she took.

If the court or jury comes to the conclusion that the defendant reasonably made a mistake, then the element of “intention” of the crime is negated potentially leading to an acquittal. 

The evidence must show that, at the moment the property was taken, the accused had made an honest mistake.

So in this example, the defendant “did” commit the crime physically but the argument here is that there was no “intentional” motivation behind the act.

Having the intention to take the property and then realizing that it was a mistake will not count as a valid defense before the criminal courts.

Mistake of Fact vs Mistake of Law

What is the difference between a mistake of fact and a mistake of law?

The mistake of “fact” is when a person makes a mistake on certain factual circumstances, events, or situations.

An example of mistake of fact is when a person misinterprets the terms of a contract and believes it to mean one thing while the other party believed it to be something else.

On the other hand, a mistake of law is when a person was unaware of the existence of certain laws at the time an event took place.

For example, a person may claim that he or she was unaware of certain traffic laws and thus made a mistake in law.

Typically, to file “mistake of law” defense in criminal cases, the defendant will need to show something along the following lines:

• The government did not publish the law for people to be aware of its existence
• The law was overturned or found unconstitutional 
• The defendant acted based on a judgment that was overruled 
• The defendant acted based on the interpretation of an official 

A mistake of law is generally not a defense as nobody should be ignorant of the law (as the old saying goes).

“Mistake of Fact” Takeaways 

So what is the legal definition of Mistake of Fact?

What is a mistake of fact defense as opposed to a mistake of law defense?

Let’s look at a summary of our findings.

Define Mistake of Fact

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