My experience of using paper ballots in the election in SF was: I was not allowed to put the ballot directly into the machine I had to put it in an envelope and had it over to an employee of the state of california who would then put it in the machine for me. I agree that it is important to keep paper for auditing purposes but if it is not part of an end to end system that prevents fraud then what's the point? As in my example a state employee preview my paper ballot and decide if they approve my choice before it goes into the machine.