What is the burden of persuasion in determining penalty?

He urges this court to revisit its decision in People v. Hayes (1990) 52 Cal.3d 577, 276 Cal.Rptr. 874, 802 P.2d 376. There we explained: "Because the determination of penalty is essentially moral and normative [citation], and therefore different in kind from the determination of guilt, there is no burden of proof or burden of persuasion. [Citation.] The jurors cannot escape the responsibility of making the choice by finding the circumstances in aggravation and mitigation to be equally balanced and then relying on a rule of law to decide the penalty issue. The jury itself must, by determining what weight to give the various relevant factors, decide which penalty is more appropriate." (Id. at p. 643, 276 Cal.Rptr. 874, 802 P.2d 376.)