Do You Trust an Opponent?


J 7 5 3
A 6 5 4 3
4
K 3 2
K 9 6 8 4 2
K J 8 10 7 2
8 7 6 3 J 9 5 2
J 7 5 10 9 5
A Q 10
Q 9
A K Q 10 Contract: 6 No trump
A Q 8 6 Opening lead: 8 of diamonds

Declarer kicked away a cold contract not just through trusting he'd located the K of spades, but worse, through trading a certainty for a possibility which couldn't have produced more tricks and perhaps even fewer. Here's what happened. The defense gave declarer a gift of sorts on that opening lead. Of course, he could have taken that same finesse himself. But would he have? In any event, declarer now went to the K of clubs and finessed the Q of spades, which held. So he went back to dummy with the A of hearts and finessed the 10 of spades, which didn't hold, and the roof caved in, as West cashed two heart tricks. Matchpoints were zero. And that's not easy to achieve.
No, it's not just hindsight that informs us that declarer had made a poor decision on going back to dummy with his last entry there to take a finesse that may or may not work. Consider this: If after the Q of spades held, declarer had banged down the A of spades and continued with the 10, there's an outside chance of four spade tricks (with a K doubleton), and a certainty of three. But on his line, he can't get more than 3 spade tricks, and might wind up with only two. (He can't get more than three because he has no more entries to dummy if the finesse holds. If the K shows up doubleton, declarer could overtake the 10, but that would mean West holds four spades, so that doesn't help. As for only two? Well, that's what he got!)
How do you like them odds? An outside chance of four with a certainty of three is traded for a maximum of three and a possibility of two! Not a good idea against any opponent. Declarer obviously would have done well to take his certainty, at which point he'd be only a 3-3 club break away from his contract. What can he gain? He goes to the A of hearts and finesses again and we'll say the 10 holds. He cashes the A of spades and drops the K on his right. That's three tricks, with, of course, no access to the J of spades.
Indeed, the wiping out of his last entry for a finesse that may or may not work was even worse than appeared at first glance. I thought for a moment that had he an extra entry, say the A of clubs along with the K, then he could reasonably take the double hook. But no. If we have the same spade distribution as above and West holds up one round and then shoots a heart through the A, on winning the second finesse, declarer must now either block the spades by winning with the A, or take a chance on East's holding that K for the setting trick.
So there was no percentage whatsoever in wiping out his last entry for a second finesse in spades. Should declarer have suspected West might be holding up? Absolutely. When the Q holds the spade finesse, what you know is that the Q held the trick. You know nothing more about the spade situation. Nor did he need to know where the K was. Even if it lies with East (originally) twice guarded and the second finesse holds, you don't get any more winners than foregoing the second finesse.