What is the test for excluding for cause a prospective juror because of their views on the death penalty?

Defendant contends the court erred in excluding for cause five prospective jurors because of their views on the death penalty, in violation of his state and federal constitutional rights. The applicable law is settled. The trial court may excuse for cause a prospective juror whose views on the death penalty would prevent or substantially impair the performance of that juror's duties. (People v. Mayfield (1997) 14 Cal.4th 668, 727, 60 Cal. Rptr.2d 1, 928 P.2d 485.) "On appeal, we will uphold the trial court's ruling if it is fairly supported by the record, accepting as binding the trial court's determination as to the prospective juror's true state of mind when the prospective juror has made statements that are conflicting or ambiguous." (Ibid.)