What is the appellate court's duty of determining reasonableness in a search and seizure case?

Since the Constitution proscribes unreasonable searches and seizures, it is the job of the courts to determine reasonableness in individual cases. The magistrate found the officers' actions were unreasonable.⁴ "Because 'that issue is a question of law,' the appellate court is not bound by the substantial evidence standard in reviewing the trial court's decision thereon. Rather, we explained, in such review it is 'the ultimate responsibility of the appellate court to measure the facts, as found by the trier, against the constitutional standard of reasonableness.' [Citation.] On that issue, in short, the appellate court exercises its independent judgment." (People v. Leyba (1981) 29 Cal.3d 591, 597, fn. omitted.)