California Code, Welfare and Institutions Code - WIC § 650

(a) Juvenile court proceedings to declare a minor a ward of the court pursuant to Section 601 are commenced by the filing of a petition by the probation officer except as specified in subdivision (b).

(b) Juvenile court proceedings to declare a minor a ward of the court pursuant to subdivision (e) of Section 601.3 may be commenced by the filing of a petition by the probation officer or the district attorney after consultation with the probation officer.

(c) Juvenile court proceedings to declare a minor a ward of the court pursuant to Section 602 are commenced by the filing of a petition by the prosecuting attorney.