Examiners don't need to absolutely rule out a cheat, they just need to be sure that a cheating examinee would not be able to absolutely rule out cheat detection

Examiners don't need to absolutely rule out a cheat, they just need to be sure that a cheating examinee would not be able to absolutely rule out cheat detection. Demonstrating absence of cheats isn't like some captcha that you just take again and again if you fail, as often as you like.