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 New Hampshire, manslaughter is categorized under RSA 630:2 as either 'Manslaughter' or 'Negligent Homicide.' Manslaughter in New Hampshire is defined as causing the death of another under circumstances that do not constitute murder, often involving a lack of premeditation or malice aforethought. It is similar to what is described as voluntary manslaughter in other jurisdictions, where the act may occur in the heat of passion or as a result of provocation. Negligent Homicide, which can be likened to involuntary manslaughter, occurs when a person causes the death of another negligently, such as by operating a vehicle under the influence of drugs or alcohol. Both offenses are considered felonies in New Hampshire, with penalties that can include imprisonment. The specific circumstances of the offense and the defendant's criminal history can influence the severity of the sentence.