There was a student who I knew was cheating, but I couldn't catch or prove it. I was not the best at that but I used to give each student a test personally so I could check the desk for notes and also so someone couldn't say there weren't enough tests in the row and then take an extra one with him or her for someone who was absent.
This happened in the 90s when I was in 103B. We were having a test on Aristotle's Poetics and Oedipus and in second period the class was full (first period was half full) and I went to hand the test to someone when she yelled out, "That is not mine, I swear it is not mine! I looked at the writing and agreed it was not in her handwriting and I commented on the fact that I recognized the person's writing. When the maintenance people cleaned the room, the desks got moved around and Jill in first period didn't get the desk with the writing. She obviously had spent time outlining the Poetics on her desk and then when she came in, her desk had been moved and she had to go it alone. She got a 46.
I said nothing to her.
We started Dante a few weeks later, and I began to talk about contrapasso, where the punishment fits the crime in Dante. Then I gave them the following "hypothetical" example:
If you were in my class and Dante wrote about you in hell. He might have a level for those who cheat on tests. The contrapasso there would be you would write the notes for Aristotle's Poetics and Sophocles Oedipus Tyrannus on your desk. Then hell's maintenance workers, drawn from mythology, would come along and move the desks. Then the next day the sinner would come in for the test and find an empty desk, her desk would have been moved, she would have to take the test without notes, and she would get a 46. This would happen over and over again throughout eternity with her always getting a 46.
Some of the kids were laughing at this example. The guilty person slid down a bit and the person next to her said very quietly, "Is she talking about you?"
She replied, "Be quiet."
I thought it was the best kind of confrontation--what I call the non-confrontation confrontation. She knew I knew she cheated and that was enough for the rest of the year.