California Code, Elections Code - ELEC § 17300

(a)(1) The elections official shall preserve all rosters or combined rosters and voter lists as provided for in Section 14107, if applicable, until five years after the date of the election, after which they may be destroyed by that official.

(2) For purposes of this subdivision, if an electronic poll book is used, a copy of the electronic data file may be preserved in lieu of preserving a paper copy of the rosters or combined rosters and voter lists, if applicable.