CA Penal Code § 1334.2 (2021)
2021 California Code|Penal Code - PEN|PART 2 - OF CRIMINAL PROCEDURE|TITLE 10 - MISCELLANEOUS PROCEEDINGS|CHAPTER 3a - Attendance of Witnesses Outside the State|Section 1334.2.

1334.2.  If a judge of a court of record in any state, which by its laws provides for commanding persons within that state to attend and testify in this state, issues a certificate under the seal of the court that there is a criminal prosecution pending in the court, or that there is a grand jury investigation, that a person within this state is a material witness in that prosecution or grand jury investigation, and that his or her presence will be required for a specified number of days, then, upon presentation of the certificate to a judge of a court of record in the county in which the person is, a time and place for a hearing shall be fixed by the judge and he or she shall make an order directing the witness to appear at the hearing.If, at the hearing, the judge determines that the witness is material and necessary, that it will not cause undue hardship to the witness to be compelled to attend and testify in the prosecution or grand jury investigation in the other state, and that the laws of the state in which the prosecution is pending or in which there is a grand jury investigation will give to the witness protection from arrest and service of civil and criminal process and will furnish in advance to the witness the sum of ten cents ($0.10) for each mile necessarily traveled if the witness elects surface travel or the minimum round trip scheduled airline fare plus twenty cents ($0.20) a mile for necessary surface travel at either end of the flight if the witness elects air travel, and, except as provided in subdivision (b) of Section 1334.3, a per diem of twenty dollars ($20) for each day that he or she is required to travel and attend as a witness and that the judge of the court in which the witness is ordered to appear will order the payment of witness fees authorized by law for each day the witness is required to attend the court plus reimbursement for any additional expenses of the witness which the judge of the court in which the witness is ordered to appear shall find reasonable and necessary, he or she shall issue a subpoena, with a copy of the certificate attached, directing the witness to attend and testify in the court where the prosecution is pending, or where the grand jury investigation is, at a time and place specified in the subpoena. In any of these hearings the certificate shall be prima facie evidence of all the facts stated therein.If the certificate recommends that the witness be taken into immediate custody and delivered to an officer of the requesting state to assure his or her attendance therein, the judge may, in lieu of notification of the hearing, direct that the witness be forthwith brought before him or her for the hearing.If the judge at the hearing is satisfied of the desirability of the custody and delivery, for which determination the certificate shall be prima facie proof of this desirability, he or she may, in lieu of issuing a subpoena, order that the witness be forthwith taken into custody and delivered to an officer of the requesting state.If the witness, who is subpoenaed as provided in this section, after being paid or tendered by some properly authorized person the sum or fare, and per diem set forth in this section, fails without good cause to attend and testify as directed in the subpoena, he or she shall be punished in the manner provided for the punishment of any witness who disobeys a subpoena issued from a court of record in this state.(Amended by Stats. 1988, Ch. 160, Sec. 133.)