A statement of an employee or agent is treated as an employer's or principal's statement and, if offered against the employer or principal, it is an admission that is exempt from the hearsay rule if the employer or principal authorized its employee or agent to speak about the matter that the employee or agent spoke about and if the statement was made during the employment or agency relationship.

Anderson v. Franklin County, 192 F.3d 1125, 1129 (8th Cir. 1999) (deaf and mute witness held to be incompetent under the circumstances).It is permissible for a trial court to disqualify a person as a witness -- to rule that a person is an incompetent witness -- because the person has a serious physical defect or infirmity that prevents the person from properly functioning as a witness.

Brown v. Bowen, 668 F. Supp. 146, 150 (E.D.N.Y. 1987) (holding, in plaintiff daughter's claim for surviving child's insurance benefits, that the written acknowledgment of paternity by Otis Fultun was admissible....If the declarant is unavailable, Federal Rule of Evidence 804(b)(4) or a comparable State rules recognizes a hearsay exception for (A) A statement concerning the declarant's own birth, adoption, marriage, divorce, legitimacy, relationship by blood, adoption, or marriage, ancestry, or other similar fact of personal or family history, even though declarant had no means of acquiring personal knowledge of the matter stated; or (B) a statement concerning the foregoing matters, and death also, of another person, if the declarant was related to the other by blood, adoption, or marriage or was so intimately associated with the other's family as to be likely to have accurate information concerning the matter declared.

Fed. R. Evid. 1004 ("The original is not required, and other evidence of the contents of a writing, recording, or photograph is admissible if-- (1) Originals lost or destroyed. All originals are lost or have been destroyed, unless the proponent lost or destroyed them in bad faith; or (2) Original not obtainable. No original can be...The best evidence rule is inapplicable -- the original writing or the original of another thing to which the rule applies -- need not be used to prove the contents of the writing or such other thing if the original is lost or destroyed through no bad faith of the proponent, the original is not obtainable, the original is in the opponent's possession and adequate notice that proof of the contents will be attempted, or the writing or other thing is not related to a controlling issue in the case.