Cal. Elec. Code § 16464
At any time within three days after the filing of the affidavit of the contestant to the effect that he or she has sent by registered mail a copy of the affidavit to the defendant, the defendant may file with the clerk of the superior court an affidavit in his or her own behalf, setting up his or her desire to have the votes counted in any precincts, designating them, in addition to the precincts designated in the affidavit of the contestant, and setting up his or her grounds therefor. On the trial of the contest all of the precincts named in the affidavits of the contestant and the defendant shall be considered, and a recount had with reference to all of those precincts. The contestant shall have the same right to answer the affidavit of the defendant as is given to the defendant with reference to the affidavit of the contestant except that the contestant's answer shall be filed not later than the first day of the trial of the contest.
Ca. Elec. Code § 16464