(1)    “Unavailability as a witness” includes situations in which the declarant:

      (a)    Is exempted by ruling of the judge on the ground of privilege from testifying concerning the subject matter of the declarant’s statement; or

      (b)    Persists in refusing to testify concerning the subject matter of the declarant’s statement despite an order of the judge to do so; or

      (c)    Testifies to a lack of memory of the subject matter of the declarant’s statement; or

      (d)    Is unable to be present or to testify at the hearing because of death or then existing physical or mental illness or infirmity; or

      (e)    Is absent from the hearing and the proponent of the declarant’s statement has been unable to procure the declarant’s attendance by process or other reasonable means.

   (2)   A declarant is not unavailable as a witness if the declarant’s exemption, refusal, claim of lack of memory, inability, or absence is due to the procurement or wrongdoing of the proponent of the declarant’s statement for the purpose of preventing the witness from attending or testifying.