TWO PLAYERS AT THE RIVER:
A bet - B call
1) A wanna muck - B can oblige him to show - Yes, because B "paid to see" A's cards... although not a formal TDA rule, this was agreed by an overwhelming # of delegates at the 2013 Summit.
Then B is beaten and wanna muck - Can A oblige him to show then? (would say yes) There is no agreement on this. Some venues require ANY hand to be shown by request, some will show the hand only until it becomes a nuisance, some are stricter and will show only with good cause. Personally I wouldn't automatically obligate B to show here, but I would obligate A for reason above.
or more simple:
2) A shows - B wanna muck - Can A obige B to show? (would say yes) See above. There is no consistency on this at the moment and IMO probably never will be. This is one place where "putting your player's hat on" makes alot of sense to me: as a player I wouldn't want to be obligated to show if I'm B in this situation.
another case:
A check - B check
3) A wanna muck - B can't oblige him to show and wins himself as the last hand without having to show neither (right?) Again, there's no clear consensus on this. Some extremely large venues / tours would require A to show here. It's basically up to your house rules at this time. What the TDA does require is that B retain his cards or have tabled them at time of his request.
4) A shows - B wanna muck - A can't oblige B to show (right?) Same answer as 3 above
another case:
THREE PLAYERS AT THE RIVER:
A bets - B calls - C calls
5) A shows - B wanna muck - Can C oblige B to show the hand? (would say yes) No consistent rule or practice on this. Personally I wouldn't automatically obligate B to show pursuant to C's request. They both paid to see A, and I would obligate A to show if either B or C requests. Note also, if C wants to see B's hand, he must retain or table his own cards at time of request.
6) A wanna muck - B oblige him to show - B shows - C wanna muck - Can B oblige C to show? (would say yes) Totally up to house rules, no consistent rule on this one. Personally, if I put my player's hat on here, if I'm C I don't think B has any special right to see my cards... we both called A.
Yet another great scenario!