Cal. Welf. and Inst. Code § 6502
A petition for the commitment of a person with a developmental disability to the State Department of Developmental Services who has been found incompetent to stand trial pursuant to Chapter 6 (commencing with Section 1367) of Title 10 of Part 2 of the Penal Code when the defendant has been charged with one or more of the offenses identified or described in Section 6500, may be filed in the superior court of the county that determined the question of mental competence of the defendant. All other petitions may be filed in the county in which that person is physically present. A petition for the commitment of a person with a developmental disability to the State Department of Developmental Services who is in acute crisis, as defined in paragraph (1) of subdivision (d) of Section 4418.7, may be filed in the superior court of the county that determined the question of acute crisis or the county in which the acute crisis home is located. The following persons may request the person authorized to present allegations pursuant to Section 6500 to file a petition for commitment:
The request shall state the petitioner's reasons for supposing the person to be eligible for admission thereto, and shall be verified by affidavit.
Ca. Welf. and Inst. Code § 6502