blackshoe, on 2011-June-15, 12:15, said:
Perhaps. But consider:
Dummy has a spade and a heart (and some diamonds, and perhaps a club or two).
Declarer (South), intending to say "heart", inadvertently says "spade". Dummy, who is thinking of a plan to dye one's whiskers green, does not move. Yet I believe we are all agreed (even pran and bluejak) that dummy's spade is a played card the moment the word "spade" passes declarer's lips.
Hence, East is not committing any irregularity when he follows suit with a spade. South now realises what he has done, and wants to correct his inadvertent designation so that North's heart and not North's spade becomes the lead to the trick.
The Director is summoned, and is convinced that South's original designation "spade" was "unintended" within the meaning of Law 45C4:
Laws of Duplicate Bridge said:
Since South has not yet played a card, the Director gives passing consideration only to the first seven words of this Law: the heart is played from dummy (who by now has completed his design to keep the Menai bridge from rust, so places the heart in the played position); East (if he wishes, or if he has a heart) changes his card; and all continue on their way rejoicing. Again, I do not believe that anyone here would dispute this procedure.
Now consider:
Events occur exactly as above, except that South plays the king of hearts to the trick before realising what he has done. He again wishes to change his original inadvertent designation, and the Director remains convinced that Law 45C4 applies as far as lack of intention is concerned.
The Director must now consider the first seven words of Law 45C4: do they mean that South cannot change his designation because South is North's partner and has played a card (the king of hearts)? That (as far as I can tell) is the view of bluejak, pran and perhaps others - and I should say here that it seems to me a perfectly sensible and practical view.
Unfortunately, it does not seem to me a legally sound view. North did not play the spade from dummy - South did that, and the card was played even though North had not physically done anything with it. For the purposes of Law 45C4, then, the "player" referred to can only be South, and "Until his partner has played a card" can mean only "Until North has played a card". Per Law 45B ( inter alia) North cannot actually play a card at all; and per Law 42A3 North (dummy) did not actually play the spade in any case (yet it was played).
So, South may change his designation after all (even if West has also played to the trick).
A question for those who consider that South may not change his designation: suppose South does not have any spades - does he still have to play the king of hearts?