“Affirmative Defense” in Criminal Law – What is it?

Posted on October 7, 2023

In criminal law, an affirmative defense is a legal defense that you, as the defendant, have the burden of proving. It does not challenge the evidence that proves the elements of the offense. Instead, an affirmative defense asserts that the crime was excusable or justified.

Examples include:

• entrapment,
• insanity,
• necessity,
• self-defense (in a couple of states),
• statute of limitations,
• mistake of fact, and
• duress.

Other affirmative defenses can defend against a civil lawsuit.

How do affirmative defenses work?

Affirmative defenses are criminal defense strategies that argue that the criminal offense being charged was somehow either:

• justified, or
• excusable.

In doing so, raising an affirmative defense silently admits that you committed the crime. Nevertheless, they argue that you should not be held accountable for it.

For example: Mark is arrested and charged with assault for punching Jerry in a fight. Mark claims that he punched Mark because he was under duress after Harry threatened to kill him if he did not punch Mark.

Importantly, it is up to you to prove an affirmative defense. You have the burden of proof and have to provide evidence that satisfies that burden.

You also have to raise an affirmative defense early on in the criminal case. You may have to raise it during the:

• arraignment, or
• preliminary hearing.

Failing to raise it early enough can be seen as a waiver of the defense.

What are some examples?

Seven examples of affirmative defenses in criminal law are:

1. entrapment,
2. insanity,
3. necessity,
4. self-defense,
5. the statute of limitations,
6. mistake of fact, and
7. duress.

1. Entrapment

Entrapment is the affirmative defense that you were induced into committing a crime that you would not have committed, but for the inducement. It prevents police or other law enforcement officers from pushing you into commit a crime.

Some examples of inducement that amount to entrapment are when police:

• pressure you into committing the crime, such as by promising a massive reward for doing it,
• harass or threaten you, or
• fraudulently insist that the conduct is legal.[1]

2. Insanity

Insanity is an affirmative defense that claims that you were insane at the time of the offense and could not have mental culpability for what you did.

Different states have different rules for determining legal insanity in a criminal case. Many, including California, follow the McNaghten Rule. In these states, you are legally insane if you did not understand either:

• the nature of the criminal act, or
• that what you were doing was morally wrong.[2]

Proving an insanity defense does not mean that you will be released. Instead, you will be committed to a mental hospital.[3]

3. Necessity

Necessity is the affirmative defense that you only committed the crime because you had to in order to prevent an even greater harm. Proving a necessity defense requires evidence that shows that:

• it was an emergency and you acted to prevent significant bodily harm or evil to someone else,
• you had no adequate legal alternative to what you did,
• you did not create a greater danger or evil than the one you avoided,
• when you acted, you actually believed that what you did was necessary to prevent harm,
• a reasonable person would also have held this belief under the circumstances, and
• you did not substantially contribute to the emergency.[4]

4. Self-defense

Self-defense is an affirmative defense to a violent crime in a few states. Where it is not an affirmative defense, you can claim that you acted in self-defense and the burden of proving otherwise shifts to the prosecutor.[5]

Where it is an affirmative defense, you would argue that you:

• reasonably believed that you or someone else was in imminent danger of harm,
• reasonably believed that the immediate use of force was necessary to defend against that danger, and
• used no more force than was reasonably necessary.[6]

Note that your right to use lethal force in self-defense may be more limited.

You should also be aware of your state’s stand-your-ground and Castle Doctrine laws.

5. The statute of limitations

State criminal laws have criminal statutes of limitation. These require law enforcement officers to file criminal charges before a set period of time expires. If they fail to do so, you can raise the statute of limitations as an affirmative defense.

The applicable statute of limitations depends on the state and the offense charged. Generally, in California, prosecutors have:

• 1 year to file misdemeanor charges,
• 3 years to file minor felony charges, and
• 6 years to file felony charges that carry more than 8 years imprisonment.[7]

However, some serious offenses, including murder, do not have a criminal statute of limitations.

6. Mistake of fact

The mistake of fact defense argues that you misunderstood a particular fact and that this prevented you from forming an intent to commit the crime. To work, though, your mistake must have been in good faith and be both:

• honest, and
• reasonable. ^[8]

This defense is rare, and you should get the legal advice of a defense lawyer before deciding to rely on it.

7. Duress

Duress is an affirmative defense that claims that you only committed the crime because you had no other choice. According to the U.S. Supreme Court, in order for this defense to work, you must generally prove that:

• you were facing an immediate threat of death or serious harm,
• you had a reasonable fear that the threat would be carried out, and
• you had no other way out of the situation but to commit the crime.[9]

Most states do not allow the duress defense to be raised against a murder charge. You may also be kept from raising the defense if you were responsible for getting into the situation where your life was put at risk.

What burden of proof has to be met?

Generally, you have the burden of proving affirmative defenses by a preponderance of the evidence. This means you have to show that the elements of the defense are more likely to be true than not in order to escape criminal liability.

How is this different from other types of legal defenses?

Regular legal defenses focus on preventing the prosecutor from proving their case beyond a reasonable doubt. They aim to present evidence that conflicts with evidence that satisfies an element of the crime. By raising a reasonable doubt about your guilt, other legal defenses try to prevent a jury from deciding that you committed the crime.

Affirmative defenses essentially admit that you committed the offense. Instead, they argue that it was legally justified or excusable.

What about in civil cases?

If you are suing someone after the defendant’s conduct harmed you, they can raise an affirmative defense. Among the most common types of affirmative defenses against civil liability that are recognized by federal district courts and most state courts in civil causes of action are:

• accord and satisfaction,
• assumption of risk,
• contributory negligence,
• estoppel,
• injury by a fellow servant,
• laches,
• res judicata, and
• waiver. [10]

Legal References:

[1] See People v. West, 139 Cal.App.2d Supp. 923 (1956).

[2] California Criminal Jury Instructions (CALCRIM) No. 3450 and California Penal Code 25 PC.

[3] See People v. Dobson, 161 Cal.App.4th 1422 (2008).

[4] See CALCRIM No. 3403.

[5] See CALCRIM No. 3470.

[6] Same.

[7] California Penal Code sections 800 and 802 PC.

[8] United States v. Martin, 753 F.3d 485 (4th Cir. 2014).

[9] See Dixon v. U.S., 126 S.Ct. 2437 (2006).

[10] Federal Rules of Civil Procedure, Rule 8(c).