I sometimes find evidence of cheating on exams but I rarely take action, I don’t have to. Almost invariably the cheaters get abysmally low grades even without penalty. Some people I know get annoyed when students without evident handicap ask for and receive special treatment such as extra time on exams. I comply without rancor as the extra time never seems to help. Over the years I have had a number of students ask for incompletes. None have ever become completes.
I call this the law of below averages.
Addendum: Any student who attempts to take advantage of my lax attitude should first reflect on the Lucas Critique. Comments are open if you have experiences to share.