murder, criminal homicide, usually distinguished from manslaughter by the element of malice aforethought. The most direct case of malicious intent occurs when the killer is known to have adopted the deliberate intent to commit the homicidal act at some time before it is actually committed. Very often, however, the law presumes the existence of malice aforethought from the circumstances, and it does not necessarily have to be proved directly. The most clear-cut case of this presumption of malice is when the killer inadvertently murders a person other than his intended victim. Here, malice is presumed if the killer intended to inflict serious bodily injury, or if he behaved with such reckless disregard of the safety of others as to betray a "depraved heart." Likewise, a killing incidentally committed in the course of a felony (e.g., robbery or rape) is deemed murder; if the felony was accomplished by more than one person, all are equally guilty of the murder, not only the actual killer. A murder that is incidental to a misdemeanor, however, is treated as manslaughter. Most states prescribe various degrees of murder. Murder in the first degree generally is a calculated act of slaying committed with malice aforethought, often requiring aggravated circumstances such as extreme brutality. It receives the severest penalty, often life imprisonment or capital punishment. Second-degree murder is a homicide committed with malice, but without deliberation or premeditation. A homicide committed without malice (as in negligent motor vehicle operation) or in the "heat of passion" (as in a quarrel which escalates to violence) is generally considered manslaughter. In some states, certain crimes that are defined as murder of a lower degree approximate more closely the definition of manslaughter in common law. In some cases, it is difficult to determine whether malice aforethought was present; consequently the governor of a state (or other chief executive) not infrequently uses his power of commutation of sentence to revoke the death penalty, and in some states the appellate courts automatically review all convictions of murder.