Partner opens a strong notrump and you hold this hand:
Before you can think about how best to explore a heart slam, RHO bids 2♣, which shows an unspecified single-suited hand. You play 2♦ as a transfer in this auction, so you bid that. After partner’s expected 2♥, RHO bids 2♠ to show their suit and you have your first decision of the auction.
You have several options here. One would be be to cuebid 3♠, planning on pulling partner’s 3NT bid to show a slam try in hearts. Your agreements also allow you to make a direct keycard ask for hearts by bidding 4♣. The argument against 4♣ is that you would rather respond to Blackwood than bid it yourself. If your partner shows one ace you could still end up at the 5-level with 3 losers or at the 6-level with 2 losers. 3♠ encourages partner to cooperate with your slam try. If they bid 3N and you pull to 4♣, they’ll have a good idea of what your hand looks like. You choose to bid 4♣ and partner responds with 4♥.
Partner bid the 2nd step, which in your partnership shows 0 or 3 keycards. You have three yourself, so partner either has none or you’re playing with some extra aces. So far this doesn’t seem like much of a problem. But what if partner bids 4♥
after a significant break in tempo (BIT)?
Usually partner is able to count their keycards in a few seconds. When you ask for keycards and partner thinks for a long time, you have gained unauthorized information. There is a good chance that partner thinks your bid meant something else. In this situation, partner might take your 4♣
as a splinter since 3♣
would already be natural and forcing. In that case, it looks like partner either had a tough decision about cooperating opposite a club splinter or was trying to decide whether your bid was indeed a splinter or something else. On probability alone it’s likely that partner has one of the aces. What can you do now?
There’s nothing you can do. If you bid 4♣
as Keycard Gerber you must abide by partner’s response. It’s clear by looking at your hand that you didn’t intend 4♣
as a splinter. It’s not impossible for partner to hold: ♠
or worse: ♠
The first will be safe in 5♥
barring a ruff, but the second has three likely losers. If you thought 4♥
was a keycard response, you would never think of bidding again. Even if you think that the odds of partner holding one of these hands are small, a substantial source for your doubt that the partnership is on the same page is due to partner’s huddle.
Taking any action other than passing in this situation is taking advantage of unauthorized information (UI) based on partner’s BIT.
In real life, the person who held the South hand bid 6♥
. She claimed that she thought 4♥
showed 2 keycards without the queen. It’s not for us to determine the veracity of her statement, but after her partner’s BIT we feel certain that she lost the benefit of doubt.