Definition
An unintentional killing of a person resulting without malice aforethought caused either by criminal negligence or during the commission or attempted commission of an unlawful act.
Criminal Negligence
The criminal negligence required for involuntary manslaughter is when defendant’s conduct creates a high degree of risk of death or serious injury beyond the tort standard of ordinary negligence.
Although gross negligence or criminal negligent conduct is required, the majority of jurisdictions in the United States do not require that the defendant be consciously aware of the risk created by his/her conduct.
Commission or Attempted Commission of Unlawful Act
Unintentional killing occurring during the commission or attempted commission of a misdemeanor which is malum in se (wrong in itself, rather than because of legislative proscription — includes all felonies, breaches of the peace, and crimes that outrage public decency) or a felony which is not of the inherently dangerous type required for felony murder, is classified as involuntary manslaughter under the misdemeanor-manslaughter rule.
On the other hand, a death resulting from a malum prohibitum crime can only be sufficient for involuntary manslaughter when the killing is either a foreseeable consequence of the unlawful conduct or amounts to criminal negligence.
Reference Desk
California Penal Code § 192:
Manslaughter is the unlawful killing of a human being without malice . . . (b) Involuntary [Manslaughter] —in the commission of an unlawful act, not amounting to a felony; or in the commission of a lawful act which might produce death, in an unlawful manner, or without due caution and circumspection. This subdivision shall not apply to acts committed in the driving of a vehicle.