How have courts treated ineffective assistance claims against counsel who failed to call a witness?

373 (9th Cir. 1997) (same); United States v. Harden, 846 F.2d 1229, 1231-32 (9th Cir. 1988) (no ineffective assistance because of counsel's failure to call a witness where, among other things, there was no evidence in the record that the witness would testify); United States v. Berry, 814 F.2d 1406, 1409 (9th Cir. 1987) (appellant failed to meet prejudice prong of ineffectiveness claim because he offered no indication of what potential witnesses would have testified to or how their testimony might have changed the outcome of the hearing).