Whenever a person is acquitted of a charge and it appears to the judge presiding at the trial wherein such acquittal occurred that the defendant was factually innocent of the charge, the judge may order that the records in the case be sealed, including any record of arrest or detention, upon the written or oral motion of any party in the case or the court, and with notice to all parties to the case. If such an order is made, the court shall give to the defendant a copy of such order and inform the defendant that he may thereafter state that he was not arrested for such charge and that he was found innocent of such charge by the court.
Source:
Section 851.85, https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=PEN§ionNum=851.85..