Can a defendant at trial confront the prosecution witness?

"A criminal defendant has the right, guaranteed by the confrontation clauses of both the federal and state Constitutions, to confront the prosecution's witnesses. [Citations.] . . . [] Although important, the constitutional right of confrontation is not absolute. [Citations.] 'Traditionally, there has been "an exception to the confrontation requirement where a witness is unavailable and has given testimony at previous judicial proceedings against the same defendant [and] which was subject to cross-examination . . . ." [Citation.]' [Citation.] Pursuant to this exception, the preliminary hearing testimony of an unavailable witness may be admitted at trial without violating a defendant's confrontation right. [Citation.]" (People v. Herrera (2010) 49 Cal.4th 613, 620-621 (Herrera).)