California Code, Government Code - GOV § 31110.2

A county may by ordinance provide that its civil service commission or equivalent body shall have the power to issue subpoenas and subpoenas duces tecum, and compensate persons subpoenaed. This power shall be exercised and enforced in the same manner as a similar power granted the board of supervisors in Article 9 (commencing with Section 25170) of Chapter 1 of Part 2 of Division 2 of this title is exercised and enforced; except that such power shall extend only to matters within the commission's lawful jurisdiction, and that committees of the commission shall not have this power, and that reasonable fees or expenses or both may be provided for by commission regulation for any or all such witnesses regardless of which party subpoenaed them.

Subpoenas shall be signed by the chairman or secretary of the commission. Any member of the commission, or any person otherwise so empowered, may administer oaths to, or take affirmations from, witnesses before the commission.