Cal. Evid. Code § 664 : CALIFORNIA EVIDENCE CODE — BURDEN OF PROOF; BURDEN OF PRODUCING EVIDENCE; PRESUMPTIONS AND INFERENCES — PRESUMPTIONS AND INFERENCES — PRESUMPTIONS AFFECTING THE BURDEN OF PROOF — Performance of official duty
It is presumed that official duty has been regularly performed. This presumption does not apply on an issue as to the lawfulness of an arrest if it is found or otherwise established that the arrest was made without a warrant.