The religious beliefs of a witness may not be used to support an inference about the truthfulness or untruthfulness of the witness.

United States v. Gabe, 237 F.3d 954, 960 (8th Cir. 2001) (upholding trial court's admission of testimony about two prior incidents of sexual abuse because it was probative as "it tends to prove [accused's] propensity to molest young children in his family when presented with an opportunity to do so...Federal Rule of Evidence 414 and comparable rules in a few States create an exception to the prohibition against "circumstantial" use of character -- the prohibition against the use of character to show conduct -- by providing that in a criminal trial for child molestation or child sexual abuse, evidence of the defendant's commission of another offense or offenses of child molestation or child sexual abuse is relevant and admissible.

Cf. Fed. R. Evid. 610 ("Evidence of the beliefs or opinions of a witness on matters of religion is not admissible for the purpose of showing that by reason of their nature the witness' credibility is impaired or enhanced.").Under some circumstances and for some purposes a person's religious beliefs or affiliation is irrelevant to the person's behavior or credibility.

Fed. R. Evid. 804(b)(1) ("Former testimony. Testimony given as a witness at another hearing of the same or a different proceeding, or in a deposition taken in compliance with law in the course of the same or another proceeding, if the party against whom the testimony is now offered, or, in a civil action or proceeding, a predecessor in...The hearsay exception for prior testimony applies only if testimony was in fact previously given.