Murder is the act of killing another human being with "malice aforethought". Malice aforethought is defined to be the intent to kill or to inflict bodily injury, either express or implied. If a deadly weapon is used, intent to kill will necessarily be implied by a court of law. Murder can be characterized as first-degree and second degree.

First-degree murder is as an unlawful killing that is both willful and premeditated, meaning that it was committed after planning or "lying in wait" for the victim.

Second-degree murder is an intentional killing that is not premeditated or planned, nor committed in a reasonable "heat of passion" or a killing caused by dangerous conduct and the offender's obvious lack of concern for human life. Second-degree murder may best be viewed as the middle ground between first-degree murder and voluntary manslaughter.

Involuntary manslaughter usually refers to an unintentional killing that results from recklessness or criminal negligence, or from an unlawful act that is a misdemeanor or low-level felony (such as DUI). The usual distinction from voluntary manslaughter is that involuntary manslaughter is a crime in which the victim's death is unintended.

Voluntary manslaughter is commonly defined as an intentional killing in which the offender had no prior intent to kill, such as a killing that occurs in the "heat of passion." The circumstances leading to the killing must be the kind that would cause a reasonable person to become emotionally or mentally disturbed; otherwise, the killing may be charged as a first-degree or second-degree murder.