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 Missouri, homicide is defined as the act of one person causing the death of another. Not all homicides are considered murder; some may be classified as manslaughter, which includes deaths caused under mitigating circumstances, or they may be justified by affirmative defenses such as self-defense or insanity. Missouri law distinguishes between different types of criminal homicide based on the perpetrator's intent and level of negligence. First-degree murder involves premeditation and intent to kill, while second-degree murder involves intent to kill without premeditation. Voluntary manslaughter typically occurs in the heat of passion and involves intent to kill but without premeditation. Involuntary manslaughter in Missouri often involves reckless behavior that leads to death, such as reckless driving or driving under the influence of drugs or alcohol. Missouri statutes provide specific definitions and penalties for these offenses, which can be found in the state's penal or criminal code.