Cal. Elections Code § 14403

(a) Immediately upon the closing of the polls and before any voted ballot is taken from any of the ballot containers, the precinct board member shall, in the presence of all persons in the room who may desire to observe them, proceed to render the unused ballots unusable in one of the following ways: (1) By drawing across its face, in ink or indelible pencil, two lines that cross each other, the cross to be more than three inches square. The precinct board member shall thereupon, immediately and before any ballots are taken from any ballot container, place all defaced ballots within an envelope or other receptacle provided for that purpose. (2) By tearing or cutting in a manner so that it is apparent that the ballot has been intentionally destroyed to prevent its use. If this method of destruction is used, it shall be done in a manner so that the serial number of the ballots is retained for the purposes of reconciliation. (3) By placing all of the unused ballots into a special container provided for that purpose. A tamperproof seal containing spaces for entering the total number of unused ballots enclosed, the beginning and ending serial numbers thereof, and signature lines for all members of the precinct board following a statement certifying that all of the ballots were placed in the container in their presence and the information on the seal is true and correct, shall be provided. After signing the seal, it shall be placed on the container in a manner so that the container cannot be opened without tearing the seal. (b) This section does not apply to elections conducted using vote centers.