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 Mexico, manslaughter is categorized as either voluntary or involuntary, aligning with the general distinction made in many states. Voluntary manslaughter in New Mexico occurs when a person kills another in a sudden quarrel or in the heat of passion, without premeditation. Involuntary manslaughter, on the other hand, happens when a person kills another unintentionally by acting negligently or without due caution and circumspection. For example, causing a fatal accident due to driving while intoxicated could be considered involuntary manslaughter. Both types of manslaughter are considered third-degree felonies under New Mexico law, with voluntary manslaughter carrying a more severe penalty due to the intentional aspect of the crime. The specific statutes detailing manslaughter offenses and penalties can be found in the New Mexico Statutes Annotated (NMSA), particularly in the criminal code sections dealing with homicide.