If the trier of fact is a jury and has been unable to reach a unanimous verdict as to what the penalty shall be, the court shall dismiss the jury and shall order a new jury impaneled to try the issue as to what the penalty shall be. If the new jury is unable to reach a unanimous verdict as to what the penalty shall be, the court in its discretion shall either order a new jury or impose a punishment of confinement in the state prison for a term of 15 years to life.
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 the prior prison term for murder of the first or second degree which subjects a defendant to the punishment of life without the possibility of parole, 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.
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 life without the possibility of parole 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 the state prison for 15 years to life.
Ca. Pen. Code § 190.05