Can the death penalty be reduced to life imprisonment without parole?

The sovereign people of this state have provided in their Constitution that "The death penalty ... shall not be deemed to be, or to constitute, the infliction of cruel or unusual punishments ...." (Cal. Const., art. I, 27, italics added.) But for his age (17) at the time of his offenses, defendant herein could have been charged with the death penalty or with life imprisonment without parole. (See Pen.Code, 190.5; People v. Davis (1981) 29 Cal.3d 814, 176 Cal.Rptr. 521, 633 P.2d 186.) If the infliction of the death penalty cannot be deemed cruel or unusual punishment under the state Constitution, how can a substantially lesser penalty be so characterized?