Cal. Welf. and Inst. Code § 5303.1
For the purposes of any hearing or jury trial held pursuant to this article, the judge of the court in which such hearing or trial is held may appoint a psychiatrist or psychologist with forensic skills. Such psychiatrist or psychologist shall personally examine the person named in the petition. Such a forensic psychiatrist or psychologist shall testify at the hearing or jury trial concerning the mental condition of the person named in the petition and the threat of substantial physical harm to other beings such person presents, and neither the professional person or his designee who petitioned for the additional period of treatment nor of the physicians providing intensive treatment shall be required, unless the person named in the petition chooses to subpoena such persons, to be present at the hearing or jury trial.
If a psychiatrist or psychologist with forensic skills is not appointed pursuant to this section the person named in the petition may, upon advice of counsel, waive the presence at the hearing or at the jury trial of the professional person or his designee who petitioned for the additional period of treatment and the physicians providing intensive treatment. In the event of such waiver, such professional person, his designee, or other physicians shall not be required to be present at the hearing if it is stipulated that the certification, supporting affidavit and records of such physicians concerning the mental condition of the person named in the petition will be received in evidence.
Ca. Welf. and Inst. Code § 5303.1