Murder is the intentional, premeditated killing of another human being. The premeditation requirement for murder was historically described in the law as “malice aforethought.”

Laws regarding murder vary from state to state, and some states have a separate criminal offense of capital murder, which usually involves the most egregious circumstances, such as killing a peace officer in the line of duty or lying in wait to ambush and kill the victim. Capital murder offenses carry a potential death penalty.

And some states use the distinction of first degree murder (done with premeditation and punishable by death or life in prison) and second degree murder (generally an intentional killing without premeditation—also known as manslaughter or voluntary manslaughter in some states).

The criminal offense of murder is generally located in a state’s statutes—often in the penal or criminal code.

In Colorado, murder is classified under different degrees with specific criteria for each. First-degree murder, as defined in Colorado Revised Statutes § 18-3-102, is the most serious form of homicide and involves the intentional and premeditated killing of another person with 'deliberation' and 'afterthought', which reflects the historical concept of 'malice aforethought'. This crime is punishable by life imprisonment or the death penalty, although Colorado abolished the death penalty for offenses committed on or after July 1, 2020. Second-degree murder, detailed in § 18-3-103, is an intentional killing that is not premeditated or planned, nor committed in a heat of passion, and carries different penalties, often a lengthy prison sentence. Colorado does not use the term 'capital murder', but the most egregious cases of first-degree murder could have been subject to capital punishment prior to the abolition of the death penalty. Manslaughter, which is a lesser homicide offense, is addressed in § 18-3-104 and involves recklessly causing the death of another person or intentionally causing or aiding another person to commit suicide. The distinctions between these offenses are critical in determining the appropriate charges and penalties in homicide cases.