The Prosecution Must Demonstrate Witness's Unavailability Prior to Allowing Former Testimony from a Previous Judicial Proceeding
In Ohio v. Roberts, 448 U.S. 56, 65-66, 100 S.Ct. 2531, 65 L.Ed.2d 597 (1980), the Court held that, based upon this constitutional requirement, a prosecutor must demonstrate a witness's unavailability prior to allowing at a criminal trial former testimony from a previous judicial proceeding.
In Roberts, the former testimony was garnered at a preliminary hearing, and the witness's preliminary hearing testimony was read to the jury at trial.
The Supreme Court explained:
The Confrontation Clause operates in two separate ways to restrict the range of admissible hearsay.
First, in conformance with the Framers' preference for face-to-face accusation, the Sixth Amendment establishes a rule of necessity.
In the usual case (including cases where prior cross-examination has occurred), the prosecution must either produce, or demonstrate the unavailability of, the declarant whose statement it wishes to use against the defendant.
The second aspect operates once a witness is shown to be unavailable.
Reflecting its underlying purpose to augment accuracy in the factfinding process by ensuring the defendant an effective means to test adverse evidence, the Clause countenances only hearsay marked with such trustworthiness that "there is no material departure from the reason of the general rule."
In sum, when a hearsay declarant is not present for cross-examination at trial, the Confrontation Clause normally requires a showing that he is unavailable.
Even then, his statement is admissible only if it bears adequate "indicia of reliability." Id.