Involuntary manslaughter is the unlawful killing of a human being without malice aforethought, either express or implied. It is distinguished from voluntary manslaughter by the absence of intention. It is normally divided into two categories; constructive manslaughter and criminally negligent manslaughter.
Constructive manslaughter is also referred to as ‘unlawful act’ manslaughter. It is based on the doctrine of constructive malice, whereby the malicious intent inherent in the commission of a crime is considered to apply to the consequences of that crime. It occurs when someone kills, without intent, in the course of committing an unlawful act. The malice involved in the crime is transferred to the killing, resulting in a charge of manslaughter.
For example, a person who runs a red light in their vehicle and hits someone crossing the street could be found to intend or be reckless as to assault or criminal damage (see DPP v Newbury[13]). There is no intent to kill, and a resulting death would not be considered murder, but would be considered involuntary manslaughter. The accused's responsibility for causing death is constructed from the fault in committing what might have been a minor criminal act.
In the United States, misdemeanor manslaughter is a lesser version of felony murder, and covers a person who causes the death of another while committing a misdemeanor – that is, a violation of law which doesn't rise to the level of a felony. This may automatically lead to a conviction for the homicide if the misdemeanor involved is a law designed to protect human life. Many violations of safety laws are infractions, which means that a person can be convicted regardless of mens rea.
Constructive manslaughter in English Law is committing an unlawful dangerous act which causes death. The associated doctrine of constructive murder, under which killing in the course of committing a felony led to a charge of murder, was abolished by the Homicide Act 1957.
There are three requirements for constructive manslaughter:
Criminally negligent manslaughter is variously referred to as criminally negligent homicide in the United States, gross negligence manslaughter in England and Wales. In Scotland and some Commonwealth of Nations jurisdictions the offence of culpable homicide might apply.
It occurs where death results from serious negligence, or, in some jurisdictions, serious recklessness. A high degree of negligence is required to warrant criminal liability. A related concept is that of willful blindness, which is where a defendant intentionally puts himself in a position where he will be unaware of facts which would render him liable.
Criminally negligent manslaughter occurs where there is an omission to act when there is a duty to do so, or a failure to perform a duty owed, which leads to a death. The existence of the duty is essential because the law does not impose criminal liability for a failure to act unless a specific duty is owed to the victim. It is most common in the case of professionals who are grossly negligent in the course of their employment. An example is where a doctor fails to notice a patient's oxygen supply has disconnected and the patient dies (R v Adomako).
In jurisdictions such as Pennsylvania, if a person is so reckless as to "manifest extreme indifference to human life", the defendant may be guilty of aggravated assault as well as of involuntary manslaughter.[19]
In many jurisdictions such as California, malice may be found if gross negligence amounts to willful or depraved indifference to human life. In such a case, the wrongdoer may be guilty of second degree murder.[citation needed]
In English law, gross negligence is the test for manslaughter. The crime was defined in R v Bateman as 'to show such disregard for life and the safety of others as to amount to a crime against the state and conduct deserving of punishment.[20] In R v Adomako the House of Lords affirmed R v Bateman, and set out the five elements required for negligence:
It is for the jury to decide what constitutes 'grossly negligent behaviour'.
Vehicular manslaughter is a class C felony which holds people liable for any death which occurs because of criminal negligence, or a violation of traffic safety laws. A common use of the vehicular manslaughter laws involves prosecution for a death caused by driving under the influence of intoxicating substances (determined by excessive blood alcohol content levels set by individual U.S. states), although an independent infraction (such as driving with a suspended driver's license), or negligence, is usually also required.[22][23]
In Wisconsin, a person who causes death with any type of motor vehicle while legally intoxicated may be liable and charged with homicide by intoxicated use of a motor vehicle. Culpability lies with the perpetrator. In 2003 the maximum prison term for conviction on that charge was reduced from 40 years to 15 years imprisonment. The length of sentence is now equivalent to a charge and conviction in Wisconsin of second-degree reckless homicide.[24] In Wisconsin, as in most states, vehicular homicide occurs when the act is not perpetrated during a felony, because driving while under the influence is not a felony.
In some U.S. states, such as Texas, intoxication manslaughter is a distinctly defined offence. A person commits intoxication manslaughter if he, or she, operates a motor vehicle in a public place, operates an aircraft, a watercraft, or an amusement ride, or assembles a mobile amusement ride while intoxicated and, by reason of that intoxication, causes the death of another by accident or mistake.[25]
Intoxication manslaughter, vehicular manslaughter and other similar offences require a lesser mens rea than other manslaughter offences. Furthermore, the fact that the defendant is entitled to use the alcohol, controlled substance, drug, dangerous drug, or other substance, is no defence.[26] For example, in Texas, to prove intoxication manslaughter, it is not necessary to prove the person was negligent in causing the death of another, nor that they unlawfully used the substance that intoxicated them, but only that they were intoxicated, and operated a motor vehicle, and someone died as a result. The same rule of law applies in New York for vehicular manslaughter in the second degree.[27]
In some U.S. states, assisted suicide is punishable as a second degree of manslaughter.[28]