Cal. Probate Code § 9631

(a) Except as provided in subdivision (b), where there is more than one personal representative, one personal representative is not liable for a breach of fiduciary duty committed by another of the personal representatives. (b) Where there is more than one personal representative, one personal representative is liable for a breach of fiduciary duty committed by another of the personal representatives under any of the following circumstances: (1) Where the personal representative participates in a breach of fiduciary duty committed by the other personal representative. (2) Where the personal representative improperly delegates the administration of the estate to the other personal representative. (3) Where the personal representative approves, knowingly acquiesces in, or conceals a breach of fiduciary duty committed by the other personal representative. (4) Where the personal representative’s negligence enables the other personal representative to commit a breach of fiduciary duty. (5) Where the personal representative knows or has information from which the personal representative reasonably should have known of the breach of fiduciary duty by the other personal representative and fails to take reasonable steps to compel the other personal representative to redress the breach. (c) The liability of a personal representative for a breach of fiduciary duty committed by another of the personal representatives that occurred before July 1, 1988, is governed by prior law and not by this section.