Hawaii Revised Statutes Division 4. Courts and Judicial Proceedings § 621-7

(a) Except as provided in subsection (c), every witness legally required to attend a state court or grand jury in any criminal case, other than a public officer or employee, shall be entitled to $20 for each day's attendance and a reasonable mileage fee to be established pursuant to rules adopted by the judiciary for each mile actually and necessarily traveled on the ground each way, including travel to and from the nearest airport when required to travel from another island or from outside the State.

In addition to witness' fees, every witness who attends a state court from:

Any per diem payment made pursuant to this subsection shall cover all personal expenses, including board and lodging, and shall be computed on the basis of quarter-day periods of time.

(b) Any police officer or other public officer or employee (except the county attorney, prosecuting attorney, or deputy county attorney or deputy prosecuting attorney), who attends a state court as a witness from a district other than that in which the court is holding session, shall be allowed the police officer's, public officer's, or public employee's travel cost and mileage fees as provided in this section. A public officer or employee, if not salaried, shall receive witness fees.

(c) Every expert witness legally required to attend a state court or grand jury in any criminal case, other than a public officer or employee, shall be entitled to reasonable applicable fees for the testimony, consultation, and preparation associated with the expert witness' testimony and attendance in court.

In addition, every expert witness who attends a state court from:

Any per diem payment made pursuant to this subsection shall cover all personal expenses, including board and lodging, and shall be computed on the basis of quarter-day periods of time.

(d) As used in this section, “expert witness” includes any witness subpoenaed on behalf of the State in a criminal case, or on behalf of a defendant at the expense of the State in a criminal case, who is subpoenaed for the witness' specialized knowledge, skill, experience, training, or education to assist a grand jury, trial jury, or judge to understand the evidence or determine a fact at issue in the case.