Cal. Code of Civil Procedure § 1283

On application of a party to the arbitration, the neutral arbitrator may order the deposition of a witness to be taken for use as evidence and not for discovery if the witness cannot be compelled to attend the hearing or if exceptional circumstances exist as to make it desirable, in the interest of justice and with due regard to the importance of presenting the testimony of witnesses orally at the hearing, to allow the deposition to be taken. The deposition shall be taken in the manner prescribed by law for the taking of depositions in civil actions. If the neutral arbitrator orders the taking of the deposition of a witness who resides outside the state, the party who applied for the taking of the deposition shall obtain a commission, letters rogatory, or a letter of request therefor from the superior court in accordance with Chapter 10 (commencing with Section 2026.010) of Title 4 of Part 4.