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 Massachusetts, manslaughter is categorized as either voluntary or involuntary, aligning with the general description provided. Voluntary manslaughter occurs when someone kills another person in the heat of passion or while in a state of temporary insanity, without premeditation. Involuntary manslaughter in Massachusetts involves the unintentional killing of another person due to reckless or wanton conduct, such as operating a vehicle under the influence of alcohol or drugs and causing a fatal accident. Both types of manslaughter are considered felonies under Massachusetts law. The penalties for manslaughter can be severe, including lengthy prison sentences. The specific statutes governing manslaughter can be found in the Massachusetts General Laws under the penal code, which details the elements of the offense as well as the potential penalties upon conviction.