(1) DEFINITION OF UNAVAILABILITY.--"Unavailability as a witness" means that the declarant:
(a) Is exempted by a ruling of a court on the ground of privilege from testifying concerning the subject matter of the declarant's statement;
(b) Persists in refusing to testify concerning the subject matter of the declarant's statement despite an order of the court to do so;
(c) Has suffered a lack of memory of the subject matter of his or her statement so as to destroy the declarant's effectiveness as a witness during the trial;
(d) Is unable to be present or to testify at the hearing because of death or because of then-existing physical or mental illness or infirmity; or
(e) Is absent from the hearing, and the proponent of a statement has been unable to procure the declarant's attendance or testimony by process or other reasonable means.
However, a declarant is not unavailable as a witness if such exemption, refusal, claim of lack of memory, inability to be present, or absence is due to the procurement or wrongdoing of the party who is the proponent of his or her statement in preventing the witness from attending or testifying.