This question is about suspected collusion so I'd like to know the rules of when a player is required to show their hand, and/or when can a player ask to see cards whether or not they are in that hand or not. Also, when is a hand considered a "paid" hand and therefore players have to show if asked?
For example, there is an all-in, a call, then a re-raise (or bet if on next street) creating a potential side pot. Is there a rule that even if the side bet is not called , that bettor/raiser has to show and take hand to showdown? Or can that player just muck without showing and let the initial all-in player take the pot? This is the type of action I've been seeing between the same 2 players. And, if mucking is allowed, can a player ask to see his hand anyway? And if mucking is allowed, I'm assuming they need to wait til the river and not muck immediately after making their bet/raise since that would be the most obvious form of collusion since they didn't even wait to see the next card. I've also seen this as well!!!
And finally, what, if any responsibility does the dealer have in spotting and/or stopping this, or at minimum, bringing it to the floor's attention?