I've heard it definitively stated on a number of occaisions that if somebody mucks their hand onto your hole cards and you aren't protecting your cards, your hand is dead too.

I see in Robert's rules that the thrown cards are dead (which seems superfluous), but I don't see any rule that the player who failed to protect his cards has a dead hand as well.

Is this a rule or a just a common misconception? Where's the support for it is a rule?

Edit: Crud, I see there's a thread on this "my cards get mucked, standard?" already. Mods, feel free to move this post to that thread or kill this thread. In the meantime, I don't see the answer there, so if anybody knows, feel free to let me know the answer.

It is true if another players mucked cards touch your unprotected then yours too are now dead.

So I've heard, but is this an actual rule? If so where?

I dealt for a while and it was a rule.

It's a rule in cardrooms where those running it don't know much about poker.

I agree with you Zetack. I think the problem arises when you cannot positively identify whose cards are whose from the backs. If you allow the folder to look at all four cards and pick out his original two you open yourself up some serious problems of collusion. So, unless there is a definitive way to determine which cards belong to who, both hands get killed.

If a player folds and his cards land on top of Player X's cards, for example, Player X's hand should still be live. But if they get mixed into it, even if it has a chip on it, then both hands would have to be declared dead. Don't forget to give the folder a serious KITN too.

i think if it is a home game that you are playing with friends, having the folder look at the cards and pick out which ones are his/hers

if you are worried about collusion at a home game find a new one

In a good cardroom there is no rule that merely touching your cards kills them. In a good room, if someone tosses there cards in and they touch your cards but there is no uncertainty as to which cards are which then your hand should not be dead. However if it is not clear which cards were your and which cards weren't (to the dealer and other players) then your hand should be dead. However I saw a very knowledgable floor person come over once and ask each player to whisper there cards to him, he then looked at the cards and gave the hand back to the player. This would be difficult to do in a home game without arousing some degree of suspicion so I wouldn't try it in a home game.

If both hands are declared dead, what prevents somebody from intentionally (but making it look accidental) mucking their cards into yours in order to kill your hand?

Perma-ban and a KITN

The fact that this sort of behavior should get you uninvited to play.

Regardless, that's why you should protect your hand.

What's to prevent a random stranger from stabbing you in the face as you walk by?