Defense (legal)

Besides contesting the accuracy of an allegation made against the defendant in the proceeding, the defendant may also make allegations against the prosecutor or plaintiff or raise a defense, arguing that, even if the allegations against the defendant are true, the defendant is nevertheless not liable. Acceptance of a defense by the court completely exonerates the defendant and not merely mitigates the liability.

The defense phase of a trial occurs after the prosecution phase, that is, after the prosecution "rests". Other parts of the defense include the opening and closing arguments and the cross-examination during the prosecution phase.

Since a defense is raised by the defendant in a direct attempt to avoid what would otherwise result in liability, the defendant typically holds the burden of proof. For example, a defendant who is charged with assault may claim provocation, but they would need to prove that the plaintiff had provoked the defendant.

Common law defenses

In common law, a defendant may raise any of the numerous defenses to limit or avoid liability. These include:

• Lack of personal or subject matter jurisdiction of the court, such as diplomatic immunity. (In law, this is not a defense as such but an argument that the case should not be heard at all.)
• Failure to state a cause of action or other insufficiencies of pleading.
• Any of the affirmative defenses.
• Defenses conferred by statute – such as a statute of limitations or the statute of frauds.
• Ex turpi causa non oritur actio – the action against the defendant arises from an illegality.
• Volenti non fit injuria – consent by the victim or plaintiff.
• In pari delicto – both sides equally at fault.
• Act of God is an unforeseeable natural phenomenon which involves no human agency due directly to natural causes which cannot be foreseen.
• Necessity harm done to prevent a greater evil is not actionable even though the harm was caused intentionally.
• Mistake whether of fact or of law is no defence to action.
• The law permits use of reasonable force to protect one's person or property. If force is used for self-defence they will not be liable for harm.
• Unclean hands.

In addition to defenses against prosecution and liability, a defendant may also raise a defense of justification – such as self-defense and defense of others or defense of property.

In English law, one could raise the argument of a contramandatum, which was an argument that the plaintiff had no cause for complaint.