What is the test for determining whether a prospective juror has a bias against the death penalty?

There is no requirement that a prospective juror's bias against the death penalty be proven with unmistakable clarity. [Citations.] Rather, it is sufficient that the trial judge is left with the definite impression that a prospective juror would be unable to faithfully and impartially apply the law in the case before the juror. [Citation.] Assessing the qualifications of jurors challenged for cause is a matter falling within the broad discretion of the trial court. [Citation.] The trial court must determine whether the prospective juror will be unable to faithfully and impartially apply the law in the case. [Citation.] A juror will often give conflicting or confusing answers regarding his or her impartiality or capacity to serve, and the trial court must weigh the juror's responses in deciding whether to remove the juror for cause. The trial court's resolution of these factual matters is binding on the appellate court if supported by substantial evidence. [Citation.] [W]here equivocal or conflicting responses are elicited regarding a prospective juror's ability to impose the death penalty, the trial court's determination as to his true state of mind is binding on an appellate court. ( People v. Gray, supra, 37 Cal.4th at pp. 192193, 33 Cal.Rptr.3d 451, 118 P.3d 496.)