|Scope of criminal liability|
|Severity of offense|
|Offence against the person|
|Crimes against property|
|Crimes against justice|
|Crimes against animals|
|Defences to liability|
|Other common-law areas|
An affirmative defense to a civil lawsuit or criminal charge is a fact or set of facts other than those alleged by the plaintiff or prosecutor which, if proven by the defendant, defeats or mitigates the legal consequences of the defendant's otherwise unlawful conduct. In civil lawsuits, affirmative defenses include the statute of limitations, the statute of frauds, waiver, and other affirmative defenses such as those listed in Rule 8 (c) of the Federal Rules of Civil Procedure. In criminal prosecutions, examples of affirmative defenses are self defense, insanity, and the statute of limitations.
In an affirmative defense, the defendant may concede that he committed the alleged acts, but he proves other facts which, under the law, either justify or excuse his otherwise wrongful actions, or otherwise overcome the plaintiff's claim. In criminal law, an affirmative defense is sometimes called a justification or excuse defense. Consequently, affirmative defenses limit or excuse a defendant's criminal culpability or civil liability.
A clear illustration of an affirmative defense is self defense. In its simplest form, a criminal defendant may be exonerated if he can demonstrate that he had an honest and reasonable belief that another's use of force was unlawful and that the defendant's conduct was necessary to protect himself.
Most affirmative defenses must be pleaded in a timely manner by a defendant in order for the court to consider them, or else they are considered waived by the defendant's failure to assert them. The classic unwaivable affirmative defense is lack of subject-matter jurisdiction. The issue of timely assertion is often the subject of contentious litigation.
Mistake of fact
"Mistake of fact" is not an affirmative defense: it does not require proof but it does introduce doubt. In mistake-of-fact defenses, the defendant asserts that his mistaken belief prevents the establishment, beyond a reasonable doubt, of the required mens rea.
The insanity plea
Among the most controversial affirmative defenses is the insanity defense, whereby a criminal defendant seeks to be excused from criminal liability on the ground that a mental illness, at the time of the alleged crime, prevented him from understanding the wrongful nature of his actions.
Burden of proof
Because an affirmative defense requires an assertion of facts beyond those claimed by the plaintiff, generally the party who offers an affirmative defense bears the burden of proof. The standard of proof is typically lower than beyond a reasonable doubt. It can either be proved by clear and convincing evidence or by a preponderance of the evidence.
In this respect, affirmative defenses differ from ordinary defenses [claim of right, alibi, infancy, necessity, and (in some jurisdictions, e.g., all U.S. states except Ohio) self-defense (which is an affirmative defense at common law)], which the prosecution has the burden of disproving beyond a reasonable doubt.
Rule 8 of the Federal Rules of Civil Procedure governs the assertion of affirmative defenses in civil cases that are filed in the United States district courts. Rule 8(c) specifically enumerates the following defenses: "accord and satisfaction, arbitration and award, assumption of risk, contributory negligence, discharge in bankruptcy, estoppel, failure of consideration, fraud, illegality, injury by fellow servant, laches, license, payment, release, res judicata, statute of frauds, statute of limitations, waiver, and any other matter constituting an avoidance or affirmative defense."
Rule 11 of the Federal Rules of Civil Procedure requires that affirmative defenses be based on "knowledge, information, and belief, formed after an inquiry reasonable under the circumstances," and cannot consist of a laundry list of all known affirmative defenses.
Affirmative vs. negating defense
An affirmative defense is different from a "negating defense". A negating defense is one which tends to disprove an element of the plaintiff's or prosecutor's case. An example might be a mistake of fact claim in a prosecution for intentional drug possession, where the defendant asserts that he or she mistakenly believed that the object possessed was an innocent substance like oregano. Because this defense simply shows that an element of the offense (knowledge of the nature of the substance) is not present, the defendant does not have any burden of persuasion with regard to a negating defense. At most the defendant has the burden of producing sufficient evidence to raise the issue.
- Civil law
- accord and satisfaction
- assumption of risk (when the plaintiff knowingly entered into a dangerous situation)
- defense of property
- contract specification
- contractual provision (when the defendant's liability for causing the plaintiff's injuries had been waived in the contract; however, these provisions are typically unconscionable in many situations.)
- contributory negligence (when the plaintiff's actions contributed to his own injury)
- fair use
- laches (similar to statute of limitation)
- merger doctrine
- statute of frauds
- statute of limitations (too much time has elapsed between the tort and the complaint)
- Criminal law
- Neubauer, David W. (2005). America's Courts and the Criminal Justice System. Wadsworth. p. 320. ISBN 0-534-62892-3.
- Brody, David C.; James R. Acker; Wayne A. Logan (2001). Criminal law. Aspen. p. 241. ISBN 0-8342-1083-5.
- "MCL 780.972". State of Michigan - Legislative Services Bureau. Retrieved February 10, 2012.
- Neubauer, David W. (2005). America's Courts and the Criminal Justice System. Wadsworth. p. 321. ISBN 0-534-62892-3.
- Oran, Daniel; Mark Tosti (2000). Oran's Dictionary of the Law. Delmar. p. 20. ISBN 0-7668-1742-3.
- Vail, Jeff (2010). "Checklist of Affirmative Defenses".
- "YouTube 'Dancing Baby' Copyright Ruling Sets Fair Use Guideline". New York Times. September 14, 2015. Retrieved 2015-09-15.