A prior statement of a witness is exempt from the prohibition against hearsay evidence if the prior statement is consistent with the witness' testimony at the trial or hearing at which the prior statement is offered, the prior statement is offered to rebut a express or implied charge of recent fabrication or motive, and the witness who made the prior statement testifies and is subject to cross-examination at the trial or hearing at which the prior statement is offered.

United States v. Lauersen, 348 F.3d 329, 340 (2d Cir. 2003) (upholding trial court's admission of nurse's statements as admission by a party's agent because (1) "nurses in [defendant] Lauersen's office were....A statement by an agent or an employee who is not authorized to speak on behalf of the agent's principal or the employee's employer may nonetheless be treated as the statement of the principal or the employer and thus as a vicarious admission that is exempt from the prohibition against hearsay; but such a statement can be imputed to the principal or the employer only if the statement, if by an agent, is about a matter within the scope of the agent's agency or, if by an employee, the statement is about a matter within the scope of the employee's employment.

Fed. R. Evid. 602 ("Evidence to prove personal knowledge may, but need not, consist of the witness' own testimony.").Evidence that a witness has the personal knowledge that is required of a witness may be provided by the witness whose testimony is offered but evidence of the witness's personal knowledge may also be provided by other witnesses or by other evidence.

United States v. Kaden, 819 F.2d 813, 818 (7th Cir. 1987) (upholding trial court's admission of statements of lounge owner/manager during the taped conversations with his girlfriend because "the 'goal' of this....A statement falls within the hearsay exemption for statements of co-conspirators only if the statement was made in furtherance of the conspiracy.