first degree murder

premeditated murder, murder which was planned in advance

Murder is the unlawful killing of one human being by another. Murder is generally distinguished from other forms of homicide by the elements of malice aforethought and the lack of justification. All jurisdictions, ancient and modern, consider it a most serious crime. Most jurisdictions impose a severe penalty for its commission.
See more at Wikipedia.org...

MURDER, FIRST DEGREE - In order for someone to be found guilty of first degree murder the government must prove that the person killed another person; the person killed the other person with malice aforethought; and the killing was premeditated.

To kill with malice aforethought means to kill either deliberately and intentionally or recklessly with extreme disregard for human life.

Premeditation means with planning or deliberation. The amount of time needed for premeditation of a killing depends on the person and the circumstances. It must be long enough, after forming the intent to kill, for the killer to have been fully conscious of the intent and to have considered the killing.

First-degree murder in California includes a killing that is "willful, deliberate, and premeditated," or that is committed in the perpetration, or attempt to perpetrate, certain felonies, including burglary, and not including the petty offense of shoplifting. Cal. Penal Code S 189.