The hearsay exceptions created by Federal Rule of Evidence 804 or a comparable State rule apply only if the declarant (the maker of the statement) is unavailable to testify at the trial or proceedings at which the declarant's statement is offered.

United States v. Silva, 380 F.3d 1018, 1020 (7th Cir. 2004) (reversing conviction for conspiracy and possession with intent to distribute methamphetamine because the trial court improperly admitted testimony of DEA....The right of confrontation guaranteed by the Sixth Amendment to the Constitution of the United States bars the introduction against a criminal defendant of testimonial hearsay by a nontestifying declarant unless (i) the absent declarant is unavailable to testify at trial and (ii) the defendant had an adequate opportunity to cross-examine the absent declarant prior to trial.

United States v. McGee, 408 F.3d 966, 982 (7th Cir. 2005) ("Although Rule 608(b) bars extrinsic evidence of specific instances of conduct bearing on a witness' character for truthfulness, the extrinsic evidence may still be admissible for another reason, such as impeachment for bias, contradiction, or...Extrinsic evidence of prior inconsistent statements is not barred by the partial federal codification in Federal Rule of Evidence 608(b) of the common law collateral matter rule.

United States v. Cerno, 529 F.3d 926, pin? (10th Cir. 2008) (conviction for aggravated sexual abuse in Indian country; defendant, invoking Fed.R.Evid. 403, contended that his conviction must be reversed because the district court improperly allowed the prosecutor to question...Subject to limitations, a witness may be impeached by a prior inconsistent statement.