What is an Affirmative Defense
An affirmative defense is a legal argument in which a defendant admits the basic facts of the accusation but presents new facts or legal reasons that justify or excuse the conduct and defeat the claim.
An affirmative defense is a legal argument in which a defendant does not simply deny the plaintiff's or prosecutor's claims, but instead introduces new facts or legal arguments that, if proven, justify or excuse the defendant's conduct and defeat the opposing party's claim — even if the underlying facts are true. The defendant essentially says "yes, but..." rather than "no, I didn't."
How Affirmative Defenses Work
Unlike a standard defense (which challenges the facts of the accusation), an affirmative defense:
- Admits (or doesn't dispute) the basic facts alleged
- Introduces new facts that change the legal outcome
- Shifts the burden to the defendant — they must prove the affirmative defense (usually by a preponderance of the evidence in civil cases, or raise a reasonable doubt in criminal cases)
Common Affirmative Defenses in Civil Law
Self-Defense
Defendant used force, but only as necessary to protect themselves from imminent harm.
Statute of Limitations
The plaintiff waited too long to file the lawsuit — beyond the legally permitted time period for that type of claim.
Consent
The plaintiff agreed to the conduct that is now the basis of the lawsuit (e.g., signing a liability waiver).
Contributory/Comparative Negligence
The plaintiff's own negligence contributed to their harm.
Assumption of Risk
The plaintiff knowingly and voluntarily accepted the risk of the activity that caused the harm.
Duress
The defendant acted under threat of serious harm and had no reasonable alternative.
Impossibility / Frustration of Purpose
In contract law — performance became impossible or pointless due to unforeseen circumstances.
Common Affirmative Defenses in Criminal Law
Insanity Defense
The defendant was suffering from a severe mental disease that prevented them from understanding the wrongfulness of their actions.
Self-Defense (Justification)
The defendant used force to protect themselves or others from imminent unlawful force.
Entrapment
Law enforcement induced or coerced the defendant into committing a crime they would not otherwise have committed.
Alibi
The defendant was not present at the scene of the crime (technically not an affirmative defense, but raises reasonable doubt).
Necessity
The defendant committed the crime to prevent a greater harm.
Duress
The defendant was threatened with imminent death or serious injury unless they committed the crime.
Procedural Requirements
In both civil and criminal cases, affirmative defenses must typically be pleaded early in the proceedings (usually in the defendant's answer or motion to dismiss). Failure to raise an affirmative defense can result in waiver — the defendant loses the right to use it.