Murder is the unlawful killing, with malice aforethought, of another human, and generally this premeditated state of mind distinguishes murder from other forms of unlawful homicide (such as manslaughter).
As the loss of a human being may inflict grief upon the individuals close to the victim, and the commission of a murder is highly detrimental to the good order within society, most societies both present and in antiquity have considered it a most serious crime worthy of the harshest of punishment. In most countries, a person convicted of murder is typically given a long prison sentence, possibly a life sentence where permitted, and in some countries, the death penalty may be imposed for such an act – though this practice is becoming less common.
At common law
According to Blackstone, English common law identified murder as a public wrong. At common law, murder is considered to be malum in se, that is an act which is evil within itself. An act such as murder is wrong/evil by its very nature. And it is the very nature of the act which does not require any specific detailing or definition in the law to consider murder a crime.
Some jurisdictions still take a common law view of murder. In such jurisdictions, precedent case law or previous decisions of the courts of law defines what is considered murder. However, although the common law is by nature flexible and adaptable, in the interests both of certainty and of securing convictions, most common law jurisdictions have codified their criminal law and now have statutory definitions of murder.
Although laws vary by country, there are circumstances of exclusion that are common in many legal systems.
• Self-defense: acting in self-defense or in defense of another person is generally accepted as legal justification for killing a person in situations that would otherwise have been murder. However, a self-defense killing might be considered manslaughter if the killer established control of the situation before the killing took place. In the case of self-defense it is called a “justifiable homicide”.
• Unlawful killings without malice or intent are considered manslaughter.
• In many common law countries, provocation is a partial defense to a charge of murder which acts by converting what would otherwise have been murder into manslaughter (this is voluntary manslaughter, which is more severe than involuntary manslaughter)
• Accidental killings are considered homicides. Depending on the circumstances, these may or may not be considered criminal offenses; they are often considered manslaughter.
• Suicide does not constitute murder in most societies. Assisting a suicide, however, may be considered murder in some circumstances.
• Killing of enemy combatants by lawful combatants in accordance with lawful orders in war, although illicit killings within a war may constitute murder or homicidal war crimes. (see the Laws of war article)
Specific to certain countries
• Capital punishment: some countries practice the death penalty. Capital punishment ordered by a legitimate court of law as the result of a conviction in a criminal trial with due process for a serious crime. The 47 Member States of the Council of Europe are prohibited from using the death penalty.
• Euthanasia, doctor assisted suicide: the administration of lethal drugs by a doctor to a terminally ill patient, if the intention is solely to alleviate pain, is seen in many jurisdictions as a special case (see the doctrine of double effect and the case of Dr John Bodkin Adams).
• A killing simply to prevent the theft of one’s property may or may not be legal, depending on the jurisdiction. In the US, such a killing is legal in Texas. In recent years, Texas has been the scene of some very controversial incidents that involved killing to protect property, that have led to discussions of the laws and social norms of the state (see Joe Horn shooting controversy). In a highly controversial case, in 2013, a jury in south Texas acquitted a man who killed a prostitute, who, after receiving $150 from the man in exchange for sex, refused to have sex with the man, and attempted to run away with his money. The man’s lawyer argued that the man was trying to retrieve property which was stolen during night time, an action which allows for the use of deadly force in Texas. The jury accepted this defense. There was major controversy in this case, due to the fact that there were questions about whether the money was in fact stolen, since the man had given it voluntarily to the prostitute, and the “contract” of prostitution is in fact an illegal contract in Texas, since both buying and selling sex are criminal offenses.
• Killing an intruder who is found by an owner to be in the owner’s home (having entered unlawfully): legal in most US states (see Castle doctrine).
• Killing to prevent specific forms of aggravated rape/sexual assault – killing of attacker by the potential victim or by witnesses to the scene; this is especially the case in regard to child rape- legal in parts of the US and in various countries
• In some parts of the world, especially in jurisdictions which apply Sharia law, the killing of a woman or girl in specific circumstances (e.g., when she commits adultery and is killed by husband or other family members) known as honor killing, is not considered a homicide. For example, in Jordan, part of article 340 of the Penal Code states that “he who discovers his wife or one of his female relatives committing adultery and kills, wounds, or injures one of them, is exempted from any penalty.”