California Code, Elections Code - ELEC § 17302

(a) The following provisions shall apply to all state or local elections not provided for in subdivision (a) of Section 17301.  An election is not deemed a state or local election if votes for candidates for federal office may be cast on the same ballot as votes for candidates for state or local office.

(b) The packages containing the following items shall be kept by the elections official, unopened and unaltered, for six months from the date of the election:

(c) If a contest is not commenced within the six-month period, or if a criminal prosecution involving fraudulent use, marking or falsification of ballots, or forgery of vote by mail voters' signatures is not commenced within the six-month period, either of which may involve the vote of the precinct from which voted ballots were received, the elections official shall have the items identified in subdivision (b) destroyed or recycled.  The packages shall otherwise remain unopened until the items are destroyed or recycled.