California Code, Government Code - GOV § 18674

Witnesses at a hearing or investigation are entitled to the same fees as are allowed witnesses in civil cases in courts of record.

An officer serving a subpoena to secure the attendance of those witnesses shall receive the same mileage as for the service by him or her of a writ or paper for the state.The fees and mileage, except in dismissal or other punitive proceedings where the service is requested by the accused, need not be prepaid.

If a witness is subpoenaed by a state agency or its representative, the Controller shall draw his or her warrant for payment of fees and mileage when the amount is duly proved by affidavit or otherwise to the satisfaction of the Controller. The Controller may charge such warrant against any proper fund of that state agency. If a witness is subpoenaed by the accused or any person other than a state agency, his or her fees and mileage shall be paid by that person and are not proper charges against any state fund.