Self-defence is a defence to conduct but for the defence, would be a crime.
As with most criminal defenses, the fact that a crime has been committed is not at issue. What is at issue is the defendant's or the accused's liability for that crime because of some reason which justifies or excuses it or which otherwise exonerates the defendant from criminal liability.
The ability for a person to escape criminal or civil liability for what would otherwise be a crime or a tort, has a long history in law.
It was recognized and articulated in Roman law as necessitas indicit privilegium quoad jura privata (from necessity spring privileges upon another's private rights).
As recognized by Francis Bacon and Broom, this Latin maxim has been incorporated into the common law.
In Halsbury's 2006 Reissue of Laws of England, the authors intelligently codify the law as follows:
"A person acting in self-defense is normally acting to prevent the commission of a crime, as it a person acting in defense of another. The test to be applied ... is (that) divorce used in self-defense ... must be reasonable in the circumstances as the defendant believed them to be.
"Provided the force used is reasonable, a person is entitled to defend not only himself or a member of his family, but even a complete stranger if the stranger is subject to an unlawful attack by others.
"Acts of self-defense are not limited to spontaneous acts done in response to actual violence, but the threat and danger must be reasonably imminent and must be of a nature which could not be met by more pacific means.
"It cannot be ruled that a person who was attacked must retreat before retaliating. A person's opportunity to retreat with safety is a factor to be taken into account in deciding whether his conduct was reasonable....
"Where the force used is unreasonable and death results, the defendant is liable to be convicted of murder or manslaughter.... No defense is available if what the defendant is defending himself or another person against is neither a criminal nor an unlawful act."
Given the significant consequences and controversial nature of this defence, and the plain fact that it can be so readily manipulated, many jurisdictions have taken to articulating the defence in their criminal law statute. For example, §34 of Canada's Criminal Code:
"Every one who is unlawfully assaulted without having provoked the assault is justified in repelling force by force if the force he uses is not intended to cause death or grievous bodily harm and is no more than is necessary to enable him to defend himself.
Every one who is unlawfully assaulted and who causes death or grievous bodily harm in repelling the assault is justified if (a) he causes it under reasonable apprehension of death or grievous bodily harm from the violence with which the assault was originally made or with which the assailant pursues his purposes; and (b) he believes, on reasonable grounds, that he cannot otherwise preserve himself from death or grievous bodily harm."
Other jurisdictions, such as the State of Texas, provide a much longer code. The Penal Code of Texas, in particular, does not allow self-defence to be used as an excuse or justification as a response to verbal provocation alone.
Australia's Criminal Code, §10.4:
"A person is not criminally responsible for an offence if he or she carries out the conduct constituting the offence in self‑defence."
But the Australia Criminal Code bans the use of the self-defence excuse if "really serious injury" occurs in the mere defence of property.
REFERENCES:
- Criminal Code, Revised Statutes of Canada 1985, Chapter C-46
- Duhaime, Lloyd, Legal Definition of Air of Reality Test
- Duhaime, Lloyd, Legal Definition of Battered Woman Syndrome
- Duhaime, Lloyd, Legal Definition of Necessitas Indicit Privilegium Quoad Jura Privata
- Duhaime, Lloyd, Self-Defence in Criminal Law
- Penal Code of Texas, §9.31 Self-Defense