There's a legal principle examined in court called -- authenticating the chain of custody.  When there's quantities of ballots, all of the sudden being found, their legitimacy should be challenged -- Were the being secretly snuk in under cover of the wee hours??  Who delivered them.  Was in the U.S. post office.  Were these from authorized couriers collected from ballot receiving boxes. 

Plenty of room for cheating unless their chain of custody can be authenticated. 

Same authentications needed all thru the earlier processing, where cart fulls are incoming.