Can a defendant confront prosecution witnesses on cross-examination?

A criminal defendant has a constitutional right to confront prosecution witnesses, but the right is not absolute. (People v. Cromer (2001) 24 Cal.4th 889, 892 (Cromer).) "An exception exists when a witness is unavailable and, at a previous court proceeding against the same defendant, has given testimony that was subject to cross-examination." (Ibid.) 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." (Id. at p. 901.)