California Code, Probate Code - PROB § 451

(a) For the purpose of appraisal of property in the estate, the probate referee may require, and may issue a subpoena to compel, the appearance before the referee of the personal representative, guardian, conservator, or other fiduciary, an interested person, or any other person the referee has reason to believe has knowledge of the property.

(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.