What's the rule here? Hand plays out, player wins. As the board is being flipped back over, the pot about to be pushed to the winner, it is discovered that the river card was from another (2nd) deck.

Roberts Rules are a bit unclear to what it means for a card with a different back to "appear" during the hand. What do you guys think?

Lets see.
Turn action complete.
Dealer knocks the table to show she is about to burn&turn.
She burns.
And there, on the top of the stub, is a card with a different colored back!
But, nobody notices.
She puts the card out as the river ...

Really?

Hand over. Results stand. Get a new set up.

Q: 53 cards in the deck? Was the "alien" card the "right" suit/value?

That's not what happened. If I were the floor I'd call the entire thing dead and give the players their money back.

You have a red backed deck.

One blue backed card.

Explain to me how the that blue backed card becomes the river card while never being the top card and never having its back visible to everyone.

Could go either way. Since the hands was over when it was discovered, I would lean towards pushing the pot as normal, then getting the decks squared away. But a ruling to void the hand and return all bets would be acceptable too.

Some rooms have one light green deck and one light blue deck. At the WSOP one year they had one dark gray deck and one darker gray deck. Can't necessarily blame anyone for not noticing if it happened in one of those rooms.

You could blame the cardroom manager who ordered them or the card manufacturer who allowed the order to be filled or the dealer who allowed the card to slip over and didn't catch it.

I'm in the "could go either way" camp as well, but lean toward voiding the hand.

You said 'top of the stub' not top of the deck. At Talking Stick the colors aren't extremely different and w/ the speed it's easy to imagine that nobody noticed.

I am pretty sure there are some rooms who would let the hand stand since the hand is over and other rooms that would void the hand because the next hand hasn't started yet.

I don't feel strongly either way and doubt there's a definitive "right" or "wrong" here. I just know I wouldn't blame another player for not noticing since I am sure I wouldn't have noticed it either. But the dealer should be asked not to work in auto-mode.

Seems like not making it stand after the fact would be exploitable.

Alternate question: Similar colored decks, alien card is in players hand (know by him/her, but not by anyone else). That player could freeroll by bluffing and having hands declared dead if called, but take it down and muck if not.

Player can play with the alien card in his hand. But if he doesn't speak up about it right away, his and only his hand is dead if it's tabled at showdown.

So if you know another player uses the alien card and want to be a d*** about it, you can freeroll him by calling him down and have his hand declared dead at showdown.

That's what the burn card is for, it did its job.

Then the dealer peels off the burn card and ?

Oh I don't know, maybe in that 1 second not everybody was staring at the hands of the dealer. If the color isn't very bright then a card is easily not noticed in that short period.

Where I play they use some setups that have 2 decks very close in color. Never understood why they'd do that when there are other color combos they could make that would have decent contrast.

Go on...

In my experience and my view of the best practice for the situation is that when a card with a different back appears in a hand all action is void and all bets are returned to the players if discovered before the start of the next hand for the current hand only. Any previous hands stand.

Once the hand is finished you need some kind of ill intent to go back and void a hand.

Imagine if the extra card were not discovered immediately, but two hands later. How late is too late?

This is well established. Once the next hand starts, the previous hand is done and cannot be undone. The next hand starts with the first riffle in a hand shuffled game, and usually when the dealer pushes the button on the machine in a auto shuffled game.

As I read the OP, the error was noticed before the next hand had begun. As such, if the presence of the foreign card is sufficient to invalidate the hand in its entirety, then it is not too late, and the hand in question is undone, and all money is returned to all players. If the presence of the foreign card is not sufficient to invalidate the hand, then it doesn't matter.

But, even if we are certain (at this point) that the foreign card had been there since the last deck change, you cannot invalidate or undue all of the prior hands before the one in question. For all of those hands, you have started the next hand, and they are therefore permanent.

At least, that is my understanding of the rules.

Cheers, Greg Raymer (FossilMan)

The part of the deck in the dealer's hand is called the stub.

I would think the action stands if the river was a blue 4 from an Uno deco if there was a bet, a call, and the dealer pushed the pot with no objections vs someone trying to free roll afterwards

I'm usually the first person to question things like "How does NOBODY at the table notice ______", but I think you're really over-estimating how easy this is to see. As other's have said, a lot of places use very similar colored decks, the back of the card is only visible for less than a second, and I would think the vast majority of players aren't really focused on making sure the back of each card is the correct color.

I agree with Fossilman's post. If this is discovered before the start of the next hand (first riffle of hand shuffle or pressing the green button on shuffler), the hand should be void.

This is mostly correct. I bolded the part that I'm not sure what Greg means by "sufficient to invalidate the hand". If the alien card is found in the stub, the results of the hand stand. If the alien card is discovered anywhere else during the hand, it is void.

In the OP: This hand should be void and all bets returned to all players. If the next hand had started, the results would stand.

It's definitely the beginning of the next hand and not the end of the current hand?

Because recalling a pushed pot is ... unpopular.

The beginning of the next hand is when the dealer does the first riffle or pushes the green button on the auto shuffler. (everywhere I know of anyway) In this case neither of those things have happened, so the next hand has not yet started. I would void the results of this hand.

Agreed. This exact scenario happened here in Detroit at the casino I play at most often. The hand was over and as the dealer spread the stub (after all betting was completed, but before the pot was shipped), they found a card from a different deck in the middle of the stub (it was Omaha so there wasn't much of a stub left). The floor here voided the entire hand due to the extra card in the deck and everyone's money was returned (with only mild debate from a couple players about if they limped preflop or not in the 2-5 PLO game before folding to a raise)