If the defendant has been found guilty of murder in the first degree, and a special circumstance has been charged and found to be true, or if the defendant may be subject to the death penalty after having been found guilty of violating subdivision (a) of Section 1672 of the Military and Veterans Code or Sections, , , or of this code, the trier of fact shall determine whether the penalty shall be death or confinement in state prison for a term of life without the possibility of parole. In the proceedings on the question of penalty, evidence may be presented by both the people and the defendant as to any matter relevant to aggravation, mitigation, and sentence including, but not limited to, the nature and circumstances of the present offense, any prior felony conviction or convictions whether or not such conviction or convictions involved a crime of violence, the presence or absence of other criminal activity by the defendant which involved the use or attempted use of force or violence or which involved the express or implied threat to use force or violence, and the defendant's character, background, history, mental condition and physical condition.
However, no evidence shall be admitted regarding other criminal activity by the defendant which did not involve the use or attempted use of force or violence or which did not involve the express or implied threat to use force or violence. As used in this section, criminal activity does not require a conviction.
However, in no event shall evidence of prior criminal activity be admitted for an offense for which the defendant was prosecuted and acquitted. The restriction on the use of this evidence is intended to apply only to proceedings pursuant to this section and is not intended to affect statutory or decisional law allowing such evidence to be used in any other proceedings.
Except for evidence in proof of the offense or special circumstances which subject a defendant to the death penalty, no evidence may be presented by the prosecution in aggravation unless notice of the evidence to be introduced has been given to the defendant within a reasonable period of time as determined by the court, prior to trial. Evidence may be introduced without such notice in rebuttal to evidence introduced by the defendant in mitigation.
The trier of fact shall be instructed that a sentence of confinement to state prison for a term of life without the possibility of parole may in future after sentence is imposed, be commuted or modified to a sentence that includes the possibility of parole by the Governor of the State of California.
In determining the penalty, the trier of fact shall take into account any of the following factors if relevant:
After having heard and received all of the evidence, and after having heard and considered the arguments of counsel, the trier of fact shall consider, take into account and be guided by the aggravating and mitigating circumstances referred to in this section, and shall impose a sentence of death if the trier of fact concludes that the aggravating circumstances outweigh the mitigating circumstances. If the trier of fact determines that the mitigating circumstances outweigh the aggravating circumstances the trier of fact shall impose a sentence of confinement in state prison for a term of life without the possibility of parole.
Ca. Pen. Code § 190.3