I'll see how this works - but I'm looking for input from other DMs and players. How have you handled cheaters in the past, if they were otherwise decent players and okay human beings?
-O
I used to have a friend in our game who was a habitual liar. He would lie to make himself seem better. He would make stuff up on the spot to try to pass off that he was an expert about something he knew nothing about. He would exaggerate things he had done when retelling them to make himself sound cooler.
In games he would lie about die rolls. His character sheet would change between sessions with higher attributes, hp, xp, and better equipment. He would buy the module the DM was running to find out where treasure was hidden and to know what monsters he would face and what NPCs he could push around with impunity.
We didn't want to boot him from the group or get into arguments all the time but it did bug us and it bugged me.
I disliked the changing of his characters. I disliked feeling that everybody else risked bad things happening to their characters but feeling that he would likely cheat his way out of them if he could (particularly when I was a player facing having bad things happening to my character). I disliked being lied to.
In reaction to this I changed the way I ran games to reduce the opportunities for cheating and lieing.
I requested die rolls from everybody in front of me so I could see them.
I would occasionally ask for a die roll by die size but not say what it was for (earlier D&D editions had some checks with high rolls for success and some requiring low rolls for success).
I would keep PC character sheets between sessions.
I would change things from the default in the modules.
I was quite happy with point buy options for character generation and when we switched to a flat amount of hp increase per level instead of rolling.
Minimizing the opportunities for cheating reduced the cheating and lieing.
I was happier for it.