What is the test for independent review of a prosecution's failure to locate and present a witness at trial?

We "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." (See People v. Cromer (2001) 24 Cal.4th 889, 901.) While Cromer speaks solely of failed efforts to locate an absent witness, there is no logical reason not to apply the independent review standard to failed efforts to obtain the attendance of a witness at trial. (See Ohio v. Roberts, supra, 448 U.S. at pp. 74-75 [requiring good-faith effort to "locate and present" the witness].)