"Manslaughter is distinguished from murder by the absence of malice, one of murder's essential elements. To establish malice or malice aforethought in a homicide prosecution, the government must prove that the defendant killed intentionally or recklessly with extreme disregard for human life."
"If the defendant killed with the mental state required for murder (intent to kill or recklessness with extreme disregard for human life), but the killing occurred in the heat of passion caused by adequate provocation, then the defendant is guilty of voluntary manslaughter. The finding of heat of passion and adequate provocation negates the malice that would otherwise attach."
"By contrast, the absence of malice in involuntary manslaughter arises not because of provocation induced passion, but rather because the offender's mental state is not sufficiently culpable to meet the traditional malice requirements. Thus, involuntary manslaughter is an unintentional killing that evinces a wanton or reckless disregard for human life but not of the extreme nature that will support a finding of malice."