Cal. PROB § 452

(a) The probate referee may: (1) Examine and take the testimony under oath of a person appearing before the referee. (2) Require, and issue a subpoena to compel, the person to produce any document in the person’s possession or control, concerning the value of any property in the estate. (b) A subpoena issued under subdivision (a) is subject to the provisions of Chapter 6 (commencing with Section 2020.010) of Title 4 of Part 4 of the Code of Civil Procedure governing deposition subpoenas.