California Code, Code of Civil Procedure - CCP § 262.8

(a) When the sheriff and coroner are both parties.

(b) When either of these officers is a party, and the process is against the other.

(c) When either of these officers is a party, and there is a vacancy in the office of the other, or where it appears, by affidavit, to the satisfaction of the court in which the proceeding is pending, or the judge thereof, that both of these officers are disqualified, or by reason of any bias, prejudice, or other cause would not act promptly or impartially.