Someone two years below me was caught using crib notes in a first year exam. They weren't challenged during the exam as it would've disturbed other candidates. They were taken to one side by the invigilators at the end of the exam to be told that both of them had seen the notes being used and that disciplinary proceedings for cheating would follow. The student withdrew from uni before anything actually happened.
TBH they'd failed more than half of their coursework and the only way they would've passed an exam would've been to cheat. They were already facing the retake of the year, so getting the hell out if Dodge was a wise move.