In People v. Cromer (2001) 24 Cal.4th 889, a case involving the appropriate standard of review for a trial court's determination of due diligence in applying the exception to a criminal defendant's right to confrontation for prior recorded testimony (Evid. Code, 1291), the Supreme Court held the appellate courts should independently review the sufficiency of the prosecution's failed efforts to locate an absent witness -- a mixed question of law and fact. The Cromer Court explained, "Mixed questions are those in which the '"historical facts are admitted or established, the rule of law is undisputed, and the issue is whether the facts satisfy the relevant statutory or constitutional standard, or to put it another way, whether the rule of law as applied to the established facts is or is not violated.'" " (Cromer, supra, 24 Cal.4th at p. 894.) "We conclude that appellate courts should independently review a trial court's determination that the prosecution's failed efforts to locate an absent witness are sufficient to justify an exception to the defendant's constitutionally guaranteed right of confrontation at trial. '. . . Independent review is . . . necessary if appellate courts are to maintain control of, and to clarify, the legal principles.' Our conclusion that a trial court's due diligence determination is subject to independent review comports with this court's usual practice for review of mixed question determinations affecting constitutional rights." (Cromer, at p. 901, citing cases involving juror misconduct, voluntariness of confessions, reasonableness of a search, validity of Miranda waivers and reasonableness of detention.) In reaching this result, the Cromer Court emphasized the trial court's resolution of any factual disputes must be reviewed under a deferential, substantial evidence standard (id. at pp. 894, 902; accord, People v. Seijas (2005) 36 Cal.4th 291, 304); "but once a trial court through its findings has determined the historical facts, it is no better situated than an appellate court to make the predominantly legal determination that those facts do or do not demonstrate prosecutorial due diligence in locating the absent witness." (Cromer, at p. 902.)