Capital murder is any homicide for which the potential punishment is death. The death penalty, or execution, is also known as capital punishment. The word "capital" is derived from the Latin word for "head," and one ancient method of executing criminals was cutting off their heads. Any time a particular type of murder can be punished by putting the murderer to death, it is capital murder, which also can be referred to as capital homicide.
The word "homicide" means taking a human life, which is often a crime, but not always. Certain homicides are considered legal or justifiable, such as killing another person in self-defense. The word "murder," however, applies only to homicides that are not legal or justifiable under the law and are punishable as crimes. Capital murders are those crimes of murder that the law will punish by its severest penalty, the death penalty.
Not all murders are capital, and in fact, not all criminal homicides are considered murders. A less severe form of homicide that is still considered a crime is often called manslaughter, which is the unlawful killing of another person through negligence or recklessness or in the heat of the moment. Murder, at least as it is defined in the common law tradition, involves what is called malice aforethought. This term describes the murderer's state of mind, or what the common law refers to as mens rea, which is Latin for "guilty mind." The state of mind required to call a killing murder, and the state of mind to which the term "malice aforethought" refers, is killing intentionally or killing recklessly with extreme disregard for human life.
Murder is often classified in various degrees, depending primarily on the particular state of mind that the murderer had. A murder usually is classified as murder in the first degree, the most serious kind of murder, when the murderer is determined to have acted deliberately with premeditated intent to kill another. That means that he or she planned or thought about the killing before doing it.
Some jurisdictions do not impose capital punishment for any crimes, and in those places, there is no capital murder. In places that do use the death penalty for certain types of murder, it typically is used only for the most severe forms of murder. These forms of murder include first degree murder; murders with specific aggravating circumstances, such as murdering a police officer; or felony capital murder, when the murder is committed as part of another serious crime, such as burglary or bank robbery. These will be considered capital crimes because those who commit them might suffer capital punishment.