After the complaining or charging party presents its evidence during its case-in-chief, an opposing party is entitled to present evidence in its own case-in-chief.

Fed. R. Evid. 415(b) ("A party who intends to offer evidence under this Rule shall disclose the evidence to the party against whom it will be offered, including statements of witnesses or a summary of the substance of any testimony that is expected to be offered, at least fifteen days before the scheduled date of trial or at such later...In a case in which a party intends to offer evidence of other sexual wrongs under a rule such as Federal Rule of Evidence 415 or a comparable State rule, the offering party may be required to disclose such evidence in advance to the party against whom such evidence will be offered.

Fed. R. Evid. 804(a)(3) (declarant is unavailable if declarant "(3) testifies to a lack of memory of the subject matter of the declarant's statement").For purposes of the hearsay exceptions created by Federal Rule of Evidence 804 or a comparable State rule, a declarant is "unavailable" within the meaning of Rule 804(a) or a comparable State rule if the declarant testifies to a lack of memory of the subject matter of the declarant's statement; but a declarant is not "unavailable" if such claim of lack of memory is due to the procurement or wrongdoing of the proponent of a statement for the purpose of preventing the witness from attending or testifying.

Marra v. Philadelphia Housing Authority, 497 F.3d 286, 298-299 (3d Cir. 2007) (holding, in plaintiff supervisors' unlawful retaliation action against defendant state agency, that the trial court properly admitted plaintiff's testimony....A statement is imputed to a principal or to an employer and is treated as the principal's or employer's vicarious admission (which, like other admissions is exempt from the hearsay rule) if the principal or employer is a party, the statement is offered against the principal or party, the statement is a statement by the party's agent or employee about a matter within the scope of the agent's agency or the employee's employment, and the statement is made during the principal-agent or employer-employee relationship.