29 C.F.R. § 18.804
(a) Definition of unavailability. Unavailability as a witness includes situations in which the declarant:
(5) Is absent from the hearing and the proponent of a statement has been unable to procure the declarant's attendance (or in the case of a hearsay exception under paragraph (b) (2), (3), or (4) of this section, the declarant's attendance or testimony) by process or other reasonable means.
A declarant is not unavailable as a witness if exemption, refusal, claim of lack of memory, inability, or absence is due to the procurement or wrongdoing of the proponent of a statement for the purpose of preventing the witness from attending or testifying.
(b) Hearsay exceptions. The following are not excluded by the hearsay rule if the declarant is unavailable as a witness:
(4) Statement of personal or family history.
(5) Other exceptions. A statement not specifically covered by any of the foregoing exceptions but having equivalent circumstantial guarantees of trustworthiness to the aforementioned hearsay exceptions, if the judge determines that—