N.H. Rev. Stat. Ann. § 521-A:6

Every deaf person whose appearance before a proceeding entitles him to an interpreter shall notify the appointing authority of his disability prior to any appearance and shall request at such time the services of an interpreter. An appointing authority may require a person requesting the appointment of an interpreter to furnish reasonable proof of his disability when the appointing authority has reason to believe that the person is not so disabled.