Cal. Bus. & Prof. Code § 6146
(a) An attorney shall not contract for or collect a contingency fee for representing any person seeking damages in connection with an action for injury or damage against a health care provider based upon such person’s alleged professional negligence in excess of the following limits:
(3) If an action is tried in a civil court or arbitrated, the attorney representing the plaintiff or claimant may file a motion with the court or arbitrator for a contingency fee in excess of the percentage stated in paragraph (2), which motion shall be filed and served on all parties to the action and decided in the court’s discretion based on evidence establishing good cause for the higher contingency fee.
The limitations shall apply regardless of whether the recovery is by settlement, arbitration, or judgment, or whether the person for whom the recovery is made is a responsible adult, an infant, or a person of unsound mind.
(c) For purposes of this section: