2 players in the hand. Does a player have to show, expose his/her hand if, at the completion of the river and final betting the calling player makes the mistake of exposing their hand first. The called player tired to muck and a heated discussion insued. The issue was resolved poorly but I am curious as to whether the player who errored in exposing early as well as other players at the table have the right to see the hand that is called no matter what the sequence is in exposing hands. This deals with tells, strategy and reading the opponents style.
The losing player is not required to expose his hand unless other players ask to see it. If the other players ask to see the hand, he is required to open it.
Some card rooms might have different rules, especially at home games. But this is what Robert's Rules of Poker says:
However you should note that it is poor etiquette to request to see a losing player's hand. This rule is in place not to satisfy your curiosity, but to empower the players to police the games and identify cheaters and collusion. Don't be that guy.