What is the test for determining whether a statement or confession was illegally obtained?

"In considering a claim that a statement or confession is inadmissible because it was obtained in violation of a defendant's rights under Miranda [], the scope of our review is well established. 'We must accept the trial court's resolution of disputed facts and inferences, and its evaluations of credibility, if they are substantially supported. [Citations.] However, we must independently determine from the undisputed facts, and those properly found by the trial court, whether the challenged statement was illegally obtained.' [Citations.] We apply federal standards in reviewing defendant's claim that the challenged statements were elicited from him in violation of Miranda. [Citations.]" (People v. Bradford (1997) 14 Cal.4th 1005, 1032-1033.) In independently determining whether the challenged statements were illegally obtained, we "'"'give great weight to the considered conclusions' of a lower court that has previously reviewed the same evidence." [Citations.]'" (People v. Whitson (1998) 17 Cal.4th 229, 248.)