The credibility of a witness may not be supported, or "bolstered," before the witness' credibility has been attacked; i.e., evidence that enhances a witness' credibility is inadmissible before an attempt has been made to impeach the witness.

United States v. Powell, 50 F.3d 94, 99-100 (1st Cir. 1995) (upholding trial court's admission into evidence of guns and ammunition from the Fairlawn Estates apartment because "this evidence was more than adequate for the court to have allowed the jury to consider whether [accused]...Evidence of another crime, wrong, or act is admissible if there is sufficient evidence to support a finding by a reasonable juror that the other crime, wrong, or act occurred. Clear and convincing evidence is unnecessary; "sufficient" means only that there must be enough evidence to make the other crime, wrong, or act relevant.

United States v. Jackson, 335 F.3d 170, 178 (2d Cir. 2003) (upholding trial court's exclusion of co-conspirator's plea allocution under Rule 804(b)(1) because (1) "[co-conspirator] was unavailable at Jackson's trial....If the declarant is unavailable, Federal Rule of Evidence 804(b)(1) or a comparable State rule creates a hearsay exception for 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 interest, had an opportunity and similar motive to develop the testimony by direct, cross, or redirect examination.

Fed. R. Evid. 807(B) (statement admissible under Rule 807 only if "the statement is more probative on the point for which it is offered than any other evidence which the proponent can procure through reasonable efforts").The hearsay exception created by Federal Rule of Evidence 807 or a comparable State rule applies only if the the affected statement is more probative on the point for which it is offered than any other evidence which the proponent can procure through reasonable efforts.