This wasn't a difficult question per se, I was just unprepared to answer it. I stumbled for a bit before responding that the best solution is to address this issue (which is pervasive) at the beginning of the semester, to include your cheating policy in the syllabus, and to ensure beforehand that you and the professor are on the same page re: consequences. Finally, if you do catch a student cheating - it should be the same consequences applied across the board. No special treatment.