Manslaughter is the unlawful killing or homicide of a human being without the premeditation or malice (malice aforethought) required for the criminal offense of murder.

Many states have two types of manslaughter: (1) voluntary manslaughter—the defendant intended to kill the victim, but did so in self-defense, or in the heat of passion and without premeditation, or the defendant was insane and did not understand that the killing was wrong; and (2) involuntary manslaughter—the defendant negligently or recklessly caused the death of another person—such as when a person is intoxicated while operating a motor vehicle and causes an accident that results in the death of another person.

Some states do not have separate criminal offenses for voluntary and involuntary manslaughter—these states may have the offense of manslaughter and identify certain aggravating factors that may enhance the penalties upon a conviction for manslaughter.

Manslaughter is a felony offense and may be punished by a lengthy prison term. Manslaughter laws are generally located in a state's statutes—often in the penal or criminal code.

In Idaho, manslaughter is defined under Idaho Code § 18-4006 and is categorized as either voluntary or involuntary. Voluntary manslaughter occurs when a person unlawfully kills another human being without malice aforethought, either upon a sudden quarrel or heat of passion. Involuntary manslaughter, as per Idaho law, involves the unintentional killing of another person while committing an unlawful act not amounting to a felony, or in the commission of a lawful act which might produce death, in an unlawful manner. Both types of manslaughter are considered felonies in Idaho. The penalties for manslaughter can vary, but they generally involve a prison sentence. The specific circumstances of the offense, such as the presence of any aggravating factors, can influence the severity of the punishment. It is important to consult with an attorney for case-specific legal advice, as the application of manslaughter laws can be complex and the consequences of a conviction are serious.