Qualification, or competence, of a person to serve as witness; evidence about the credibility of witnesses and hearsay declarants: impeachment and rehabilitation

See United States v. Safavian, 435 F. Supp. 2d 36, 38-42 (D.D.C. 2006) ("The requirement of authentication or identification as a condition precedent to admissibility is satisfied by evidence sufficient to support a finding that....A thing or matter is sufficiently authenticated to be admissible in evidence if the authenticating evidence submitted to the trial court is sufficient -- strong enough -- to permit a reasonable jury or reasonable trier of fact to conclude that the proffered thing or matter is authentic, that the proffered thing or matter is what its proponent claims it is.

Fed. R. Evid. 405(a) advisory committee's note ("According to the great majority of cases, on cross-examination inquiry is allowable as to whether the reputation witness has heard of particular instances of conduct pertinent to the trait in question. Michelson v. United States, 335 U.S. 469, 69 S.Ct. 213, 93 L.Ed. 168 (1948); Annot., 47...Although a character witness who testifies to the reputation of another person or gives an opinion of the character of another person cannot testify to specific instances of that person's conduct to bolster the character witness's testimony, an opposing party may question the character witness about specific instances of the person's conduct to show that the character witness' testimony about the character of the person was not well-founded.

United States v. Mercado Irizarry, 404 F.3d 497, 501 (1st Cir. 2005) (upholding trial court's admission of statements from a conspirator about defendant's involvement in a murder because "there was adequate evidence that the....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.