Murder is the unlawful killing of another human person with malice aforethought, as defined in Common Law countries. Murder is generally distinguished from other forms of homicide by the elements of malice aforethought and the lack of lawful justification. All jurisdictions, ancient and modern, consider it a most serious crime and therefore impose severe penalty on its commission.

Legal analysis of murder

Common law murder is defined as the: 1. unlawful 2. killing 3. of another human person 4. with a state of mind known as "malice aforethought."

The first three elements are relatively straightforward; however, the concept of "malice aforethought" is a complex one that does not necessarily mean premeditation. The following states of mind are recognized as constituting the various forms of "malice aforethought":

(i) Intent to kill; (ii) Intent to inflict serious bodily harm short of death; (iii) Reckless indifference to an unjustifiably high risk to human life (sometimes described as an "abandoned and malignant heart"); or (iv) Intent to commit a dangerous felony (the "felony-murder" doctrine).

Under state of mind (i), intent to kill, the deadly weapon rule applies. Thus, if the defendant intentionally uses a deadly weapon or instrument against the victim, such use authorizes a permissive inference of intent to kill. An example of a deadly weapon or instrument is a gun, a knife, or even a car when intentionally used to strike the victim.

Under state of mind (iii), an "abandoned and malignant heart," the killing must result from defendant's conduct involving a reckless indifference to human life and a conscious disregard of an unreasonable risk of death or serious bodily injury. An example of this is a 2007 law in California where an individual could be convicted of second-degree murder if he or she kills another person while operating a motor vehicle while being under the influence of alcohol, drugs, or controlled substances.

Under state of mind (iv), the felony-murder doctrine, the felony committed must be an inherently dangerous felony, such as burglary, arson, rape, robbery or kidnapping. Importantly, the underlying felony cannot be a lesser-included offense such as assault, otherwise all criminal homicides would be murder as all criminal homicides are felonies.

Murder in religion

One of the oldest known prohibitions against murder appears in the Sumerian Code of Ur-Nammu written sometime between 2100 and 2050 BC. The code states, "If a man commits a murder, that man must be killed."

In Abrahamic religions, the prohibition against murder is one of the Ten Commandments given by God to Moses in (Exodus: 20v13) and (Deuteronomy 5v17) (See Murder in the Bible). The Vulgate and subsequent early English translations of the Bible used the term secretly killeth his neighbor or smiteth his neighbour secretly rather than murder for the Latin clam percusserit proximum.