[Vampyr]

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3♣ was alerted and explained as a mixed raise. After receiving this explanation, North doubled. The actual agreement was fit jump.

So... in the play, is declarer allowed to know that North has clubs? He has doubled to show them, but this double was based on misinformation. I asked a director who is much more experienced than I, and he said that North's holding clubs was authorised to declarer, because the auction is always authorised. But I wonder...

This post has been edited by Vampyr: 2011-February-21, 09:47

[blackshoe]

Quote

Law 16A1(a): A player may use information in the auction or play if: (a) it derives from the legal calls and plays of the current board (including illegal calls and plays that are accepted) and is unaffected by unauthorized information from another source;

Note that "the auction is always authorized" is not a true statement. So the question here is whether the information that North has hearts is affected by UI. There is UI here: East's explanation that 3♣ is a mixed raise is UI to West. But East doesn't have any UI, and he's the declarer. So it seems to me the answer to your question is "yes, declarer is allowed to know that North has hearts".

[Cascade]

That maybe true in a temporal sense.

However at the end of the hand north maybe able to argue MI which would have induced him not to double and therefore not to give the opponents so much information thus causing damage.

[blackshoe]

That may be, Wayne, but it is not relevant to the original question.

[bluejak]

Actually, Ed, I think it is. If declarer assumes he knows something from the auction, but that something is a direct result of MI from his side, therefore declarer should be aware that using that information is not productive because it is likely to be ruled back at the end. So, in effect, best - and ethically best as well - is to act as though you did not know it.

So while the technical answer as to whether you are allowed to know it may be Yes, the practical answer is No.

[iviehoff]

(Crossposted with Bluejak's) I don't think this (ie Blackshoe's analysis) can be correct. W would not know N has hearts if it was behind screens. It worries me that W is allowed to know something as AI simply because it is open rather than screened.

Suppose this was behind screens. E would misinform North about 3♣, and discover in return that double shows hearts. But W would correctly inform S and get a different explanation of the double. Has W been misinformed? I think not. N has misbid on the basis of MI, and W has received the correct explanation. W therefore declares the contract, knowing the "correct" explanation, but not the fact of N's misbid.

So I think the correct answer is as follows.

The AI to W is "if W has a fitjump, dbl shows A, if W has a mixed raise, dbl shows B". Since "N thinks W has a mixed raise" is UI, knowledge that N was misbidding on the basis of MI is UI, so W is not allowed to use the knowledge that N has hearts. Even if he heard S say it, and not give the full explanation as above.

This post has been edited by iviehoff: 2011-February-21, 08:11

[Vampyr]

Sorry!!!!! This is really embarrassing. I don't know how I managed to type that North has hearts, of course he has clubs, and that is what he doubled to show when he thought the bid was artificial!

[Vampyr]

blackshoe, on 2011-February-20, 19:39, said:

But East doesn't have any UI, and he's the declarer.

He will have UI before the play of the hand when partner tells the opponents that the agreement was that 3♣ is a fit jump.

So now, according to the "actual" auction, the doubles does not show clubs.

[Cyberyeti]

If declarer had been W, there would have been more of an issue.

E has made his explanation (wrongly), and N has bid on that basis. NS may claim damage afterwards, but I think declarer can assume N has clubs in the play.

If W had been declarer, he doesn't see his partner's explanation, so assumes the unalerted double is takeout of his fit jump so may not be able to assume this. But then of course what happens if he simply asks what the double is ...