Law 75B (Misbid and forgetting system)
No bids were announced or alerted.
3C was bid as a weak jump overcall in clubs, but systemically should have been a Ghestem bid showing at least 5-4 in spades and diamonds (no point count suggested). South responded in accordance with the system agreement, with 3S simply showing at least 4 cards support. 3S however was taken as a good spade suit by North as they had forgotten the system, so raised to 4S over the 4H bid.
Assuming that the auction to 4H is unaffected, the question becomes would East, given the benefit of the doubt, double with their cards knowing that NS are playing Ghestem? If not, would West still bid 5H or would pass and/or double be appropriate? Ghestem was included in NS's opening remarks at the start of the first board of their set, but this was the second board of the set so they had forgotten, and in any case isn't a reason to prevent redress as per Law 75B.
My personal view is that 5Hx (which went off 1 at the table) should be adjusted to 4Sx by South which will comfortably go off (the exact number of tricks is irrelevant for the MP score). That said, this wouldn't always happen and there's also an argument to be made that EW shouldn't have ended up in 5H in spite of the undisclosed system information (also, while not really a double shot situation, it might be worth considering). I certainly don't think that the result at the table should just stand but there is an argument to be made for a weighted score of some kind.
Comments
Having read it through again, I certainly don't think this is a double shot situation. I also feel that either East or West could have directed the auction to 4Sx even without full information and that reaching 5H on this auction is partially their fault. Something like 75% for 4S (doubled or passed out, again irrelevant for the MP score) going down and 25% for 5Hx-1 seems about right.
I suppose you have to start with a couple of questions...
1 - Yes, they are playing guesstem and it was not alerted as it should have been
2 - It does not seem like there was - S responded as if N had both majors and N raised under the belief that partner had their own spade suit.
3 - I'm not sure and I think that a number of similar standard players using the E/W system would need to polled to establish that.
Personally, if you said that the system was alerted correctly throughout, and was just misbid/phyched, then would the ops have bid differently? If I recall correctly, the ops are not allowed to know that NS have had a bidding misunderstanding, unless it becomes obvious from the bidding.
Maybe with a correct alert, east would more fully value his spades, 4 to the KQ as the supposition would be that N had the good spade holding. As it was, it looks like S has the spade holding for that the KQxx is not so good. Would that be enough for E to change their pass over 4S to a double? West is assuming that N/S have a good spade fit, would that be affected by an alert? One possible point there, is that if correctly advised that 3C was Ghestem , showing 5-4 in the majors... W has 6H, but had only opened (not sure if this is a 4CM or 5CM open) but partner supported to 3H. How many would this show Hx or 3+ or 4+? This then raises alarm bells, N has shown min 4H, W has 6 and E has raised H so has some. This means that W would either start to question the validity of 3C from N, or would assume that they are not making many defensive tricks in H suit due to S's supposed shortness.
I don't think it is terribly clear what action W would do that is different? His defense to 4S with the information that N has both majors does not look great. If W went to 5H thinking N had length in C and a fit in S, would they bid differently? If E cannot find a double of 4S here, would he find a double with the correct information that N has both majors?
I think that there would need to be 2 polls - one for E first, to see if he doubles 4S with the correct information. Then another for W, so see if they double if E passes, or what is his action if E doubles (pass or bid 5H)?
The Ghestem bid showed diamonds and spades, not both majors.
Sorry misread that. So showing S and D... essentially the same questions arise ...
From W's hand, on the bidding and the correct explanation that N has S and D, where are is defensive tricks? no S, possibly 1 H, maybe 1 or possibly 2 D assuming S could be short... 1C. So a double of 4S would be based on making 2D tricks, or partner taking 1+ tricks in defense.
From E's hand would he now double assuming that they have 1H, no Diamond, unknown C and hopefully 2S.
There is also the point that W's 1H was in 3rd seat, so what is there bidding style like in that position. If possibly light, does the 4H bid make it stronger?
I am not sure that any of that is clear cut. So polls?
I'm not overly familiar on the pair's particular bidding style but I don't think they are likely to open light in 3rd seat. Equally, the Ghestem bid here would not be intended as a particularly weak bid, and South's response is constructive as opposed to pre-emptive.
From East's position first, when North has a known weak hand with clubs, the spades are as you say less well placed. NS are in a known 5-3 fit and are likely to have a loser in each suit (give or take), which doesn't make it a good double, especially as 5H looks attractive (partner will have a singleton spade with a ruffing finesse position, probably no heart losers and the chance to ruff any diamond losers). Giving West the option to bid 5H or double seems right in this case. When North has shown 5-4 in spades and diamonds, East now appears to have 2 spade tricks, possibly a diamond ruff or a heart trick and not an unreasonable chance of a club trick or ruff. Crucially though, 5H is now much more precarious (there is no ruffing finesse option most likely and the diamond singleton is less valuable; It is also far more likely than EW will suffer club losers off the top). East is therefore more likely to double to avoid putting West to the choice of what to do. I'm not saying that will happen but the increased likelihood at this stage is already sufficient for a weighted score.
From West's position, they do have a very defensive hand but 5H well may make for a good MP score. I'm not convinced a Ghestem bid makes much difference to their decision here; That said, if East makes a double because of the knowledge that North is showing a 5-4 hand, West has enough defence for it to be worthwhile to stick with East's decision. It's also worth noting that West's singleton club is sufficient for them to know that North had forgotten the Ghestem convention so is likely to double out of principle.
One final point to note, and I think the director can use that to make a decision, is that West asked for an explanation of 3C, first before bidding 4H and then before bidding 5H. On both occasions North failed to answer. That does suggest that they were considering an alternative action.
I was probably a little hasty to suggest 100% or 75%... that said, I do think that a ruling in favour of the non-offending side here is justified. Polls-wise, I think the above gives away my thought process but at the table, it could be closer to a flip of a coin. I'd like to think though that if I was sat West, I would piece the error of NS together and put in a double, whereas without the Ghestem knowledge I would probably bid 5H just because East hasn't doubled and needs very little for 5H to make. As East, I may well double in both situations, but a double with the Ghestem knowledge is easier.