I was the technical election judge at an Illinois polling location. Voters had their choice from two voting options - optical scan paper ballots, or touch screen.
In both cases there was a paper record of the vote. The touch screen machine prints the voter’s selections and the printed out selections can be seen by the voter on a tape visible through a window to the side of the touch screen. A physical verification could be conducted on each of the individual touch screen ballots.
What do you do if a voter says that the tape doesn't match the votes he just casted?
Is there a random audit of the tape to see if it matches the total the machine gives at the end of the night?