Self-defense usually refers to the use of violence to protect oneself and is a possible justification for this otherwise illegal act.

Its legal status varies from area to area. Courts generally find that the degree of violence used in self-defense must be comparable to the threat faced, so that deadly force should only be used in situations of "extreme" danger. Many have ruled that self-defense is only acceptable as a legal defense when the user doesn't have sufficient chance to flee. However, the castle exception (see: Edward Coke) argues that one cannot be expected to retreat from one's own home.

The concept of "pre-emptive" self-defense (for example, murdering a person believed to someday attack with lethal force) is considered dubious.

Self-defense formed the basis of numerous martial arts, but many are presently much less focused on it than they were in days of old. Such styles as karate, kung fu and tae kwon do are more focused on the sports, show, and traditional aspects of the arts, although many good schools also teach self defense classes. Surprisingly few ones teach real fighting techniques for self-defense. From the martial arts practiced world-wide two such styles are Brazilian jiu jitsu, and Krav Maga.

In politics, the concept of national self-defense against a war of aggression refers to defensive wars and is a possible cause for a just war.

Self-defense law in England

English law provides for the right of people to act in a manner that would be otherwise unlawful in order to preserve the physical integrity of themselves or others or to prevent any crime. It is provided in both common law and more specifically in the Criminal Law Act (1967). If such a defence is proved to the satisfaction of the court then the person is fully acquitted of the charges against them.

The act of protection must fulfill a number of conditions in order to be lawful. The defendant must believe, rightly or wrongly, that the attack is imminent. While a pre-emptive blow is lawful the time factor is also important, if there is an opportunity to retreat or to obtain protection from the police the defendant should do so - demonstrating an intention to avoid violence. However the defendant is not obliged to leave a particular location even if forewarned of the arrival of an assailant.

The other key factor is reasonableness - the defendants response must be necessary and in proportion to the nature of the attack. The harm inflicted on the assailant must not exceed the harm being avoided by the defendant. However like imminency the nature of the defence rests on the defendant's belief, whether their actions were in proportion to the circumstances they believed existed.

See also

• Abuse defense
• Self-defence (law)