North passed and partner (East) opened the hand 1S. As West, I had 4 choices:
- Jacoby 2NT showing 4 trumps and forcing to game
- 3S showing 4 spades and an invitational hand
- 3H (fit-jump) showing good hearts, 3+ spades and an invitational hand
- 4C showing 4 trumps, club shortness and 12-14 points.
At the table, I forgot about option #3.
I decided to upgrade my hand and splinter with 4C. Partner, with no wastage in clubs, got excited and we ended up one level too high, in 5S. When spades turned out to be 3-1, we were down 1. Everyone else in the room was bidding and making 4S.
Splinters are very well-defined bids and are there to help you find slams holding fewer than 30 high card points. Because of this, though, they work only when you stay within the parameters. Just add one point to my hand to make it 12 points (by changing the J of spades to the Q of spades) and note that 5S is totally safe. Add 3 points to my hand (by changing the Jack of diamonds to the Ace of diamonds) and note that 6S is on whenever spades are 2-2 (a 52% slam).
We would not have had this disaster if I had upgraded my hand and bid Jacoby 2NT. Partner with a semi-balanced minimum would have bid 4S.
Don't upgrade to a splinter.