When you register to vote, your ID is checked then. Then the voters dept checks the registration and assigns you to a precinct. Your name is added to the precinct voters book. When you show at the precinct, you sign your name and it is compared to the one in the book that comes from your registration. If it agrees, you then vote. When you finish, your name is marked off in the book as voted. It is a very good system that has been checked over and over and illegal votes are extremely rare. You can not vote twice. A mail-in can not be counted because you are marked as voted. If you try the authorities will soon pay you a visit.