(5) is absent from the hearing and the proponent of the declarant's statement has been unable to procure the declarant's attendance (or in the case of a hearsay exception under subdivision (b) (2), (3), (4), or (5), of this rule, the declarant's attendance or testimony) by reasonable means including process. A declarant is not unavailable as a witness if his exemption, refusal, claim of lack of memory, inability, or absence is due to the procurement or wrongdoing of the proponent of his statement for the purpose of preventing the witness from attending or testifying.