Is there any case law supporting the argument that a jury always has the power to determine the appropriate penalty?

I do disagree with the statement in People v. Boyde (1988) 46 Cal.3d 212, 253, 250 Cal.Rptr. 83, 758 P.2d 25 quoted by the majority, ante, at page 755 of 275 Cal.Rptr., at page 1185 of 800 P.2d that "when jurors are informed that they have discretion to assign whatever value they deem appropriate to the factors listed, they necessarily understand they have discretion to determine the appropriate penalty." This is not a statement of law, but of fact--of how jurors in fact reason in capital trials--and is unsupported by empirical evidence.