|Part of the common law series|
|Insanity · Immunity · Mental disorder
Intoxication · Infancy
Automatism · Alibi
Consent · Mistake
Duress · Necessity
Provocation · Self defense
False confession · Entrapment
Criminal law and procedure
|Other common law areas|
|Criminal · Contract · Tort
Property wills · Trusts and estates
|Law · Criminal justice|
|Note: Varies by jurisdiction|
|Assassination · Child murder
Contract killing · Felony murder rule
Honour killing · Human sacrifice
Lust murder · Lynching
Mass murder · Murder–suicide
Proxy murder · Lonely hearts killer
Serial killer · Spree killer
Torture murder · Feticide
Double murder · Misdemeanor murder
Crime of passion · Internet homicide
|in English law
|Note: Varies by jurisdiction|
|By victim or victims|
The United States' concept of justifiable homicide in criminal law stands on the dividing line between an excuse, justification and an exculpation. In other words, it takes a case that would otherwise have been a murder or another crime representing intentional killing, and either excuses or justifies the individual accused from all criminal liability or treats the accused differently from other intentional killers.
The normal rule in the criminal law is that those accused of crime should be convicted of an offense only if they have committed the actus reus (the Latin for "guilty act") of an offense, accompanied by the necessary mens rea (the Latin for "guilty mind") element. Thus, if one person has killed another, intending to do so, the normal consequence would be a conviction for murder. But, for a variety of different public policy reasons, societies over the centuries have considered it morally acceptable and/or merely expedient for one person to kill another and to treat this killing as "justifiable" in a number of different situations. Thus, the Laws of Solon forming part of early Athenian law, provided that if an accused pleaded that they were justified in killing another, their case would be tried in a dedicated court called the Delphinion where, for example, it was considered justifiable homicide to kill an adulterer caught in the act or a burglar caught in the act at night. These exceptions to liability match the modern concepts of provocation and defense of property and reflect the fact that, although the terminology of justification may change over the centuries, the human concepts of jealousy and the rights of ownership remain reasonably consistent as potential excuses.
In deciding when intentional killings should be treated as "justifiable", governments are balancing different sets of interests. On the one hand, states usually accept some form of practical responsibility to protect their citizens from harm. In more modern times, this reflects a social contract where allegiance is rewarded by the provision of policing and other civil defense systems, and the apparatus of redress for injuries suffered through a court system. In the United Nations Universal Declaration of Human Rights, Article 3 states that everyone has the right to life, liberty and security of person, and many constitutions offer protection for "life" which, presumably, even applies to those who have broken the law. Yet, more modern cultures also value and respect individual autonomy, and wish to avoid unduly restricting an individual's freedom of action and refrain from interfering in a citizen's life unless it is absolutely necessary. Where the balance is struck will be reflected in which situations are allowed to become excuses and result in an immunity, and those situations which merely exculpate, i.e. allow special treatment either by reducing the charge to one less serious, or by reducing the sentence. Hence, in eighteenth century English law, it was considered a justifiable homicide if a husband killed a man "ravishing" or raping his wife (Blackstone, Wm. at p391), but most modern English law jurisdictions treat this as only a circumstance that will mitigate murder to a conviction for manslaughter. In other words, the socialization of modern men (or in Nietzsche's terms, the herd-animalization or effeminization) is supposed to result in less violent responses to provocations.
Potentially excusing conditions common to most jurisdictions include the following.
A non-criminal homicide, usually committed in self-defense or in defense of another, may be called in some cases in the United States. A homicide may be considered justified if it is done to prevent a very serious crime, such as rape, armed robbery, or murder. The assailant's intent to commit a serious crime must be clear at the time. A homicide performed out of vengeance, or retribution for action in the past, would generally not be considered justifiable.
In cases of self-defense, the defendant should generally obey a duty to retreat if it is possible to do so. In the states of Alabama, Alaska, Arizona, California, Colorado, Connecticut, Florida, Georgia, Hawaii, Indiana, Kentucky, Louisiana, Maine, Maryland, Massachusetts, Michigan, Mississippi, Missouri, Montana, New Jersey, North Carolina, Ohio, Oklahoma, Oregon, Rhode Island, South Carolina, Tennessee, Texas, West Virginia, Washington, Wyoming and other Castle Doctrine states, there is no duty to retreat in certain situations (depending on the state, this may apply to one's home, business, or automobile, or to any public place where a person is lawfully present). Preemptive self-defense, cases in which one kills another on suspicion that the victim might eventually become dangerous, is considered criminal, no matter how likely it is that one was right. Justifiable homicide is a legal gray area, and there is no clear legal standard for a homicide to be considered justifiable. The circumstances under which homicide is justified are usually considered to be that the defendant had no alternative method of self-defense or defense of another than to kill the attacker.
Two other forms of justifiable homicide are unique to the prison system: the death penalty and preventing prisoners from escaping. To quote the California State Penal Code (state law) that covers justifiable homicide:
Although the above text is from Californian law, most jurisdictions have similar laws to prevent escapees from custody.