---
title: "Involuntary Manslaughter"
type: Legal Rule
source: https://casebriefly.com/legal-rules/involuntary-manslaughter
---

# Involuntary Manslaughter

Involuntary manslaughter is an unintentional killing caused by criminal negligence or during the commission of an unlawful act not amounting to a felony. It represents the least culpable form of criminal homicide.

## Definition

Involuntary manslaughter is the unintentional killing of another person through criminal negligence or during the commission of an unlawful act that does not rise to the level of a dangerous felony (which would trigger felony murder). It occupies the lowest rung of criminal homicide, below both murder and voluntary manslaughter, reflecting the absence of intent to kill or subjective awareness of a high probability of death.

Criminal negligence, the more common basis for involuntary manslaughter, requires a gross deviation from the standard of care that a reasonable person would exercise. It is more culpable than civil negligence, requiring a higher degree of risk and a more significant departure from reasonable behavior. Courts often describe it as conduct showing a wanton or reckless disregard for human life, though importantly, the defendant need not have been subjectively aware of the risk (distinguishing it from reckless conduct). Examples include deaths caused by grossly negligent driving, failure to provide medical care, or unsafe handling of firearms.

The misdemeanor-manslaughter rule (sometimes called the unlawful act doctrine) imposes involuntary manslaughter liability when a death occurs during the commission of a misdemeanor or a non-dangerous felony that does not qualify for the felony murder rule. This parallels the felony murder rule but at a lower level. Some jurisdictions limit this to malum in se offenses (inherently wrongful acts) rather than malum prohibitum offenses (acts wrong only because prohibited by statute). The Model Penal Code categorizes unintentional killings based on the mental state: reckless homicide is manslaughter, while negligent homicide is a separate, lesser offense.

## Elements

- An unintentional killing of another person
- Caused by criminal negligence (gross deviation from reasonable standard of care)
- Or caused during the commission of an unlawful act not amounting to a dangerous felony
- Criminal negligence requires more than ordinary civil negligence
- Under MPC: reckless killing is manslaughter; negligent killing is the lesser offense of negligent homicide

## Key Case

Commonwealth v. Welansky, 316 Mass. 383 (1944)

## Landmark Cases

| Name | Citation | Significance |
| --- | --- | --- |
| Commonwealth v. Welansky | 316 Mass. 383 (1944) | Upheld involuntary manslaughter conviction for a nightclub owner whose negligence in blocking exits led to deaths in the Cocoanut Grove fire |
| State v. Williams | 4 Wash. App. 908 (1971) | Convicted parents of involuntary manslaughter based on ordinary negligence for failing to provide medical care to their sick child |
| People v. Hall | 999 P.2d 207 (Colo. 2000) | Held that skiing recklessly resulting in a fatal collision could constitute reckless manslaughter |

## Exam Tips

- Distinguish criminal negligence from civil negligence; criminal negligence requires a gross deviation from reasonable conduct
- Differentiate involuntary manslaughter from depraved heart murder; depraved heart requires extreme recklessness creating a very high risk of death
- Under the MPC, distinguish between reckless manslaughter (subjective awareness of risk) and negligent homicide (failure to perceive risk)
- For misdemeanor-manslaughter, check whether the jurisdiction limits the doctrine to malum in se offenses

## Common Mistakes

- Confusing involuntary manslaughter with voluntary manslaughter; involuntary is unintentional, while voluntary involves intentional killing under provocation
- Equating criminal negligence with ordinary negligence; the criminal standard requires a substantially higher degree of deviation from reasonable conduct
- Failing to distinguish between depraved heart murder and reckless involuntary manslaughter; the difference is the degree of risk and recklessness

## Mnemonic Or Memory Aid

"Unintentional but Unreasonable" -- involuntary manslaughter involves no intent to kill but conduct so unreasonable it rises to criminal negligence

## Related Rules

- homicide-degrees-of-murder
- voluntary-manslaughter-heat-of-passion
- felony-murder-rule
- actus-reus

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Source: [Involuntary Manslaughter — CaseBriefly](https://casebriefly.com/legal-rules/involuntary-manslaughter)