WellSpyder, on 2013-October-17, 09:50, said:
Playing for ♦J to drop under the Ace? Playing ♦ from the top because he has forgotten the Jack is still outstanding?
Law 70E, broadly, prevents you from taking a finesse unless failure to do so would be irrational. It does not prevent you from taking a finesse. The TD has to decide what is irrational for the class of player in question. If you think that he thinks the jack of diamonds has been played, then you would rule as you do. I do not think playing for a doubleton jack is rational, however, even for a beginner. Or you would rule that with AQ doubleton opposite xx in a side suit, a declarer, who had miscounted his tricks, could start with the ace first.
If declarer's only sensible line is a finesse, he is allowed to take it.
I prefer to give the lawmakers credit for stating things for a reason - barmar