A nonconstitutional privilege sometimes must yield to a criminal defendant's Sixth Amendment right to confront and cross-examine an adverse witness in a criminal trial. A nonconstitutional privilege privilege may have to yield to a criminal defendant's Confrontation Right when the privilege shields evidence or facts (particularly evidence or facts showing bias) that have significant probative value on the credibility of an adverse witness in a criminal trial who testifies about material facts in issue.

Wolfle v. United States, 291 U.S. 7, 14 (1934) (petitioner, on certiorari, sought review of the judgment of the Circuit Court of Appeals affirming his conviction and permitting statements petitioner made in a letter written by him to his wife to be admitted into evidence; judgment affirmed; "The basis...It has been said that the purpose of the privilege for confidential marital communications is to foster intimate communications between spouses.

United States v. Bustamante, 493 F.3d 879, 890-891 (7th Cir. 2007) (upholding trial court's admission of a telephone conversation because "the conversation between Estremera and Corral was in furtherance of the conspiracy....A statement falls within the hearsay exemption for statements of co-conspirators only if the statement was made in furtherance of the conspiracy.

United States v. Rivera, 527 F.3d 891, 906 n. 4 (9th Cir. 2008) ("While Defendants contend that the DEA failed to properly minimize two intercepted conversations between Rigoberto and Edith Iniguez, they do not contend that Rigoberto and Iniguez were married or had a common-law marriage-only that they...The necessary predicate for either the confidential marital communications privilege ("marital secrets" privilege) or the adverse spousal testimony privilege ("marital testimony privilege" or "anti-marital facts privilege") is the existence at some time of a legally-recognized marriage.