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 is considered dubious due to common misconception of the act as murdering a person believed to someday attack with lethal force. Realistic "pre-emptive" self defense is simply the act of landing the first-blow in a situation that has reached a point of no hope for de-escalation or escape. Many self-defense instructors and experts believe that if the situation is so clear-cut as to feel certain violence is unavoidable, the defender has a much better chance of surviving by landing the first blow and gaining the immediate upper hand to quickly stop the risk to their person.

Self-defense formed the basis of numerous martial arts, especially East Asian martial arts, which usually provide self defense classes as part of their curricula.

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 the United Kingdom

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 defendant's 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 immanency, the nature of the defence rests on the defendant's belief of whether their actions were in proportion to the circumstances they believed existed.

Self-defense law in the United States

While the statutes defining the legitimate use of force in defense of a person vary from state to state, the general rule makes an important distinction between the use of physical force and deadly physical force. A person may use physical force to prevent imminent physical injury, however a person may not use deadly physical force unless that person is in reasonable fear of serious physical injury or death. Most if not all statutes also include a duty to retreat , wherein deadly physical force may only be used if the person acting in self-defense is unable to safely retreat. As discussed above, a person is generally not obligated to retreat if in one's own home (for example, a person doesn't have to retreat from the living room to the kitchen, then to the bedroom, then to the bathroom).

See also

• Abuse defense