California Code, Penal Code - PEN § 1329

(a) When a person attends before a magistrate, grand jury, or court, as a witness in a criminal case, whether upon a subpoena or in pursuance of an undertaking, or voluntarily, the court, at its discretion, if the attendance of the witness be upon a trial may by an order upon its minutes, or in any criminal proceeding, by a written order, direct the county auditor to draw his warrant upon the county treasurer in favor of such witness for witness' fees at the rate of twelve dollars ($12) for each day's actual attendance and for a reasonable sum to be specified in the order for the necessary expenses of such witness. The court, in its discretion, may make an allowance under this section, or under any appropriate section in Chapter 1 (commencing with Section 68070), Title 8, of the Government Code, other than Section 68093. The allowances are county charges.

(b) The court, in its discretion, may authorize payment to such a witness, if he is employed and if his salary is not paid by his employer during the time he is absent from his employment because of being such a witness, of a sum equal to his gross salary for such time, but such sum shall not exceed eighteen dollars ($18) per day. The sum is a county charge.

A person compensated under the provisions of this subdivision may not receive the payment of witness' fees as provided for in subdivision (a).