Cal. Gov. Code § 68097
Witnesses in civil cases may demand the payment of their mileage and fees for one day, in advance, and when so demanded may not be compelled to attend until the allowances are paid except as hereinafter provided for employees of the Department of Justice who are peace officers or analysts in technical fields, peace officers of the Department of the California Highway Patrol, peace officer members of the State Fire Marshal's Office, other state employees, trial court employees, sheriffs, deputy sheriffs, marshals, deputy marshals, district attorney inspectors, probation officers, building inspectors, firefighters, and city police officers. For the purposes of this section and Sections 68097.1 to 68097.10, inclusive, only, the term "peace officer of the California Highway Patrol" shall include those persons employed as vehicle inspection specialists by the Department of the California Highway Patrol, the term "firefighter" has the definition provided in Section 50925, and a volunteer firefighter shall be deemed to be employed by the public entity for which he or she volunteers as a firefighter.
Ca. Gov. Code § 68097