Self-defense

Self-defense (self-defence in English spelling) is a countermeasure that involves defending the well-being of oneself or of another from harm. The use of the right of self-defense as a legal justification for the use of force in times of danger is available in many jurisdictions, but the interpretation varies widely.

Physical

Physical self-defense is the use of physical force to counter an immediate threat of violence. Such force can be either armed or unarmed. In either case, the chances of success depend on a large number of parameters, related to the severity of the threat on one hand, but also on the mental and physical preparedness of the defender.

Unarmed

Many styles of martial arts are practiced for self-defense or include self-defense techniques. Some styles train primarily for self-defense, while other martial or combat sports can be effectively applied for self-defense. Some martial arts train how to escape from a knife or gun situation, or how to break away from a punch, while others train how to attack. To provide more practical self-defense, many modern day martial arts schools now use a combination of martial arts styles and techniques, and will often customize self-defense training to suit the participants' lifestyles, occupations, age groups and gender, and physical and mental capabilities.

Right of self-defense

The right of self-defense (also called, when it applies to the defense of another, alter ego defense, defense of others, defense of a third person) is the right for persons to use reasonable force or defensive force, for the purpose of defending one's own life or the lives of others, including, in certain circumstances, the use of deadly force.

Theory

The early theories make no distinction between defense of the person and defense of property. Whether consciously or not, this builds on the Roman Law principle of dominium where any attack on the members of the family or the property it owned was a personal attack on the pater familias – the male head of the household, sole owner of all property belonging to the household, and endowed by law with dominion over all his descendants through the male line no matter their age. The right to self-defense is phrased as the principle of vim vi repellere licet ("it is permitted to repel force by force") in the Digest of Justitian (6th century).

Self-defense (United States)

In the United States, self-defense is an affirmative defense that is used to justify the use of force by one person against another person under specific circumstances.

General rule

In the U.S., the general rule is that "[a] person is privileged to use such force as reasonably appears necessary to defend him or herself against an apparent threat of unlawful and immediate violence from another." In cases involving non-deadly force, this means that the person must reasonably believe that their use of force was necessary to prevent imminent, unlawful physical harm. When the use of deadly force is involved in a self-defense claim, the person must also reasonably believe that their use of deadly force is immediately necessary to prevent the other's infliction or great bodily harm or death. Most states no longer require a person to retreat before using deadly force. In the minority of jurisdictions which do require retreat, there is no obligation to retreat when it is unsafe to do so or when one is inside one's own home.