West cashes the K♣️ and then switches to the 3♠️.
Dummy (North) wins the K♠️ and leads the J♥️.
East discards 4♦️ on this first ♥️ trick.
South wins the A♥️ and then cashes the K♥️.
Here are the North/South hands at trick 5:
it seems like a good time to start finessing. Which finesse are you starting with–♠️s or ♦️s?
[The K♠️ has already been played.]
Start with diamonds. East’s discard of the four diamond suggested he does not have the queen. And lead of the three spades by West would be unlikely away from the queen. On the other hand, on the principal of open spaces, east should have both!
I wouldn’t try the spade finesse because if it works I am on the board where I don’t want to be. So the diamond finesse seems best.
Declarer has both a spade loser and a diamond loser.
If the spade finesse loses (50% chance), declarer still must take the diamond finesse.
If the diamond finesse loses as well (25% probability), then declarer goes down.
There is never a need to take the spade finesse.
A 100% line of play is to float the ♦️J at trick 5.
If West has ♦️K and plays it at first or second trick, keep on taking diamond tricks to pitch the spade loser. There is no fear that East will ruff. If and when West ruffs, his forced club or spade exit will put you on the board to cash a winning diamond upon which to discard the spade loser. Making 5.
If the ♦️K is with the East, East must win now, else South’s diamond loser is now a winner.
Trick 5, then, is the second trick for the defense.
What can East play back at trick 6?
A spade into dummy’s remaining major tenace? No, because that eliminates South’s spade loser immediately.
A minor card? Won in dummy, North cashes top diamonds to pitch South’s spade loser. West can ruff in any time, but the ♠️A provides the entry to the good diamonds.
Along with the ♥️Q then, that is 3 tricks for the defense, and 10 tricks are always makeable.
p.s. Even if East has the ♦️K and all 6 diamonds, it does West no good to ruff ♦️J in front of the Ace at trick 5, because that trick is East natural spade trick, and ruffing would telescope the defense’s natural remaining diamond and heart winners into a single trick. Any which way, 10 tricks are there for NS.
simple – D J. Whether or not D finesse works, have a pitch for spade looser.