Common Law

Involuntary manslaughter occurs when a person performs a normally lawful action, but does so without the proper care expected of a reasonable person, and someone dies as a result of that action.

Involuntary manslaughter is distinguishable from voluntary manslaughter (heat of passion manslaughter), and is typically graded as a less serious offense.

The degree of negligence required for a finding of involuntary manslaughter is typically called criminal or gross negligence, and must be a significant deviation from the expected norm. Criminal negligence is higher than the negligence standard used in torts.

Criminal negligence is distinguishable from reckless manslaughter, which involves an actor who is aware of the risk but proceeds anyway.  The criminally negligent actor is not aware of the risk, but should have been.

Some common law jurisdictions recognize a misdemeanor-manslaughter rule (which is similar to the felony-murder rule).  Under this rule, an accidental homicide that occurs during commission of a misdemeanor will be characterized as involuntary manslaughter, even if the prosecution cannot establish criminal negligence. Many jurisdictions limit this rule by requiring that the misdemeanor be inherently dangerous. In some jurisdictions where the felony-murder rule only applies to specific felonies, homicides occurring during non-listed felonies will be treated as involuntary manslaughter. Thus, it might be more appropriate to refer to an “unlawful act-manslaughter” rule rather than a “misdemeanor-manslaughter” rule.

Model Penal Code

The MPC classifies as a criminal homicide any unjustifiable, inexcusable killing committed with purpose, knowledge, recklessness, or negligence. See MPC 210.1(1).

The MPC divides criminal homicide into three categories: murder, manslaughter, and negligent homicide. Murder is a criminal homicide done intentionally, knowingly, or with depraved indifference. The MPC does not grade murder, and eliminates the “malice aforethought” element of common law murder.

The MPC eliminates the felony-murder rule: it presumes extreme recklessness if a homicide occurs during the scope of a felony, but this presumption is rebuttable and not conclusive. See MPC 210.2(1)(b).

Manslaughter under the MPC is: (1) a homicide committed recklessly (but without extreme indifference), or (2) a homicide that would otherwise constitute murder, but is accompanied by an “extreme mental or emotional disturbance” (EMED), which has a “reasonable explanation or excuse.” See MPC 210.2.

Depraved indifference murders are also reckless homicides (which means that an individual charged with depraved indifference homicide is entitled to a jury instruction on reckless homicide as well).

An EMED claim has both a subjective and an objective component. The actor must subjectively experience an EMED, and the reason for the EMED must be objectively reasonable from the point of view of someone in the actor’s “situation” (which adds a partially subjective component to this evaluation). Note that the reasonableness requirement is a judgment of whether the EMED is reasonable, not whether the homicide is reasonable.  The meaning of “the actor’s situation” is not clearly defined, but it does not include normative judgments of social groups or classes (such as a racism, sexism, or homophobia).

EMED is much broader than a common law heat of passion claim. Unlike the predicate event required for a heat of passion claim, an EMED might result from a conflux of factors. Additionally, EMED does not require that the victim be personally responsible for the EMED in any way. There is no specified list of events actions that can legally provoke an EMED, and “mere words” can be sufficient. Finally, the EMED doctrine does away with the sudden requirement from heat of passion, meaning there is no clear “cooling off” rule.

To illustrate the difference between EMED and heat of passion, suppose that Jane killed her coworker, Mary, because Mary was given a promotion that Jane was hoping to receive.  This circumstance would not qualify for either an EMED claim or a heat of passion claim. However, suppose that Jane’s child was dying from a rare disease, and Jane had been counting on the raise to help with medical cost and to keep up payments on her mortgage.  The combined impact of these factors might be enough to justify an EMED finding.

Note: EMED is distinct from a claim of “diminished capacity.” In a diminished capacity claim, a defendant argues that he was, for whatever reason, incapable of possessing the requisite mens rea. For example, an individual who sexually assaults a woman, delusionally believing her to be his consenting wife, is acting under a diminished capacity. An EMED claim admits to the requisite mens rea (and hence is inconsistent with a diminished capacity claim) but instead argues that the actor had a diminished rationality.

Homicide committed negligently, no matter how gross the negligence, never qualifies as involuntary manslaughter under the MPC. It is instead graded as a separate lesser offense, called negligent homicide.