California Code, Elections Code - ELEC § 16402

When the reception of illegal votes is alleged as a cause of contest, it is sufficient to state generally that in one or more specified voting precincts illegal votes were given to the defendant, which, if taken from him or her, will reduce the number of his or her legal votes below the number of legal votes given to some other person for the same office.

Testimony shall not be received of any illegal votes, unless the contestant delivers to the defendant, at least three days before the trial, a written list of the number of illegal votes, and by whom given, which he or she intends to prove.  No testimony may be received of any illegal votes except those that are specified in the list.