Evidence to rehabilitate a witness after impeachment must be relevant to the impeaching evidence: the rehabilitation evidence must have some tendency to diminish the force of the impeachment evidence.

United States v. Sinclair, 109 F.3d 1527, 1536-1537 (10th Cir. 1997) ("Although Rule 602 provides that a witness's testimony must be based on personal knowledge, it 'does not require that the witness' knowledge be positive or rise to the level of absolute certainty. Evidence is inadmissible ... only if...A person has the personal knowledge that a witness must have if and only if the evidence is sufficient to permit a reasonable trier of fact to conclude that the witness personally perceived the matter. The preliminary question of personal knowledge is governed by the standard of whether the evidence is sufficient to allow a reasonable person to conclude that the person has personal knowledge; the applicable standard is not the more demanding preponderance of the evidence standard.

Fed. R. Evid. 703 ("unless the court determines that [the] probative value [of inadmissible facts or data] in assisting the jury to evaluate the expert's opinion substantially outweighs their prejudicial effect").Although an expert who relies on inadmissible hearsay for his or her opinion testimony should not be allowed to disclose such hearsay to the jury when giving his or her opinion testimony, the trial court should allow such hearsay to be revealed to the jury if the trial court determines that the probative value of such hearsay in assisting the jury to evaluate the expert's opinion substantially outweighs the prejudicial effect of disclosing such hearsay to the jury.

United States v. Jimenez, 513 F.3d 62, 81 (3d Cir. 2008) (upholding trial court's admission of the tax abstracts and tax returns because "[t]he Government did not use the tax returns for the truth of the matter....The Sixth Amendment Confrontation Clause places no limits on the admission at trial of nonhearsay statements made prior to or outside of trial.