Since you dont know him, and you suspect he's cheating, and it sounds like most of the group suspect he's cheating and its beginning to affect their enjoyment, the best thing to do would be to kick him from the group. If he's not cheating, it's the best for him too - since he's never going to be trusted now, it's better for him to find a new group and start over with a clean slate. And if he is cheating, maybe he'll learn his lesson. (Probably not though.) Bear in mind: you aren't obligated to let people into your game. You can eject them for any reason at all. Ideally, you'd only do this when there are problems, but - to use a less serious example - a player not fitting in with a group is good enough reason to politely tell them so, and continue without them. Having strong suspicions a player is cheating, to the extent that it's spoiling the game for several players, is a very good reason to let someone go. You don't need to gather proof. Suspicion, and the effect on other players, is enough.