affirmative defense

An affirmative defense is a defense in which the defendant introduces evidence, which, if found to be credible, will negate criminal liability or civil liability, even if it is proven that the defendant committed the alleged acts. The party raising the affirmative defense has the burden of proof on establishing that it applies. Raising an affirmative defense does not prevent a party from also raising other defenses. 

Self-defense, entrapment, insanity, necessity, and respondeat superior are some examples of affirmative defenses.

Under the Federal Rules of Civil Procedure Rule 56, any party may make a motion for summary judgment on an affirmative defense.

There is some dispute as to whether certain defenses are actually affirmative defenses, or just standard defenses. For example, in Florida self-defense is an affirmative defense but in Ohio, it is not. 

[Last updated in June of 2022 by the Wex Definitions Team]