Haw. Rev. Stat. § 21-9: Notice to witnesses.

(a) Service of a subpoena requiring the attendance of a person at a hearing of an investigating committee shall be made at least five days prior to the date of the hearing unless a shorter period of time is authorized by majority vote of all the members of the committee in a particular instance when, in their opinion, the giving of five days notice is not practicable; but if a shorter period of time is authorized, the person subpoenaed shall be given reasonable notice of the hearing, consistent with the particular circumstances involved.

(b) Any person who is served with a subpoena to attend a hearing of an investigating committee also shall be served with a copy of the resolution or statute establishing the committee, a copy of the rules under which the committee functions, a general statement informing the person of the subject matter of the committee's investigation or inquiry, and a notice that the person may be accompanied at the hearing by counsel of the person's own choosing.