Although United States Supreme Court precedent establishes that in some circumstances a nonconstitutional privilege must yield to the federal constitutional rights of a criminal defendant, apart from the specific circumstances for which the Court has given an authoritative answer, it is unsettled and and it is unknown when such a privilege rule must yield to a federal constitutional right such as confrontation, due process, or the right to present a defense.

United States v. Withorn, 204 F.3d 790, 795 (8th Cir. 2000) (conviction for sexual abuse, including aggravated sexual abuse; accused argued that the district court erred in admitting evidence of his past sexual assault while excluding evidence that victim had falsely accused another man of raping her;...Rape shield laws limit the introduction in trials involving charges or claims of sexual assault or sexual misconduct, of evidence of the sexual disposition or other sexual conduct of an alleged victim of a sexual assault or sexual misconduct.

Feltrop v. Delo, 46 F.3d 766, pin? (8th Cir. 1995) (murder; trial court did not abridge criminal defendant's right to due process by ruling that six-year-old child, defendant's daughter, was incompetent to testify for the defense; the child was supposedly an eyewitness).A person may be disqualified from serving as a witness because of severe defects in the person's understanding or intelligence.

Fed. R. Evid. 801(d)(2)(E) ("A statement is not hearsay if-- ... (2) Admission by party-opponent. The statement is offered against a party and is ... (E) a statement by a coconspirator of a party during the course and in furtherance of the conspiracy.").A statement by a co-conspirator of a party is not barred by the hearsay rule from being admitted against the party if the statement was made by the co-conspirator during the course and in furtherance of the conspiracy.