If someone has voted an absentee ballot and then shows up to vote in person, the check-in system will alert the poll worker that the person has already voted.
The record of an absentee ballot request, as well as the actual absentee ballot, are attached to the voter's record. If a voter submits multiple absentee ballot request forms, they will still only receive one ballot because both requests are attached to a single voter record. Once a voted absentee ballot is returned, it is recorded on the voter's record. The record of a returned ballot is reflected on the poll book at one-stop early voting locations as well as on election day. If a voter appears that has already cast an absentee ballot, their record will indicate such, and the voter will not be issued a regular ballot.