Homicide is the act of one person causing the death of another person. Not all homicides are murder—some are manslaughter due to mitigating circumstances—and some are lawful when justified by an affirmative defense such as self-defense or insanity.

Criminal homicide generally involves (1) intent to cause death or serious bodily injury, or (2) negligence that causes the death of another person. Criminal homicide committed with the intent to cause death or serious bodily injury is generally charged as the criminal offense of murder (committed with intent and with premeditation or malice) or as voluntary manslaughter or second degree murder (committed with intent but without premeditation or malice).

And criminal homicide caused by negligence is generally charged as the criminal offense of involuntary manslaughter—for example, when a person is driving recklessly or speeding and hits another motor vehicle or pedestrian, causing the death of the other motorist or the pedestrian. A person driving a motor vehicle while intoxicated by drugs or alcohol who hits another motor vehicle or pedestrian, causing the death of the other motorist or the pedestrian, may be charged with involuntary manslaughter, or with a more specific offense like intoxication manslaughter or vehicular homicide—depending on applicable state laws.

Criminal homicide laws vary from state to state—including the names, degrees of severity, and punishments. These laws are generally found in a state’s statutes—often in the penal or criminal code.

In Arizona, homicide encompasses various degrees of severity based on the circumstances surrounding the death of another person. Homicide that is intentional and premeditated is typically charged as first-degree murder, which is the most serious form of homicide and can result in life imprisonment or the death penalty. When the intent to kill is present but without premeditation, the charge may be second-degree murder. Manslaughter in Arizona is a lesser charge than murder and includes situations where the death is caused under circumstances that would otherwise be murder but are committed in the heat of passion or in a sudden quarrel. Involuntary manslaughter, which Arizona law refers to as negligent homicide, occurs when a person's negligent actions lead to the death of another, such as in the case of reckless driving or driving under the influence. Arizona law also recognizes justifiable homicide, such as in cases of self-defense, where the killing is not subject to criminal charges. The specific statutes detailing homicide laws in Arizona can be found in Title 13 of the Arizona Revised Statutes.