[Cyberyeti]

I've seen several cases where the construct along the lines of "Imagine there were screens present", was used in the discussion. Does this have any basis in the laws or where does it come from ?

I'm thinking of trying to write a fairly simple "This is what UI is, these are your obligations, and this is how it should be dealt with" article for the county newsletter (Norfolk sure as hell needs this for both players and directors), and want to make sure I get my facts right.

[blackshoe]

It's not in the laws.

[jallerton]

 Cyberyeti, on 2011-April-06, 13:31, said:

I've seen several cases where the construct along the lines of "Imagine there were screens present", was used in the discussion. Does this have any basis in the laws or where does it come from ?

It's not in the Laws per se, but the concept of "Imagine there were screens present" is useful in determining what your logical alternatives are based solely on the available authorised information. If you decide that you, and your peers, would not have considered any alternative action to call Y, had you been playing with screens, then the Laws permit to choose action Y when playing without screens, even if you have UI which could demonstrably suggest action Y.

[Cyberyeti]

 jallerton, on 2011-April-06, 15:56, said:

It's not in the Laws per se, but the concept of "Imagine there were screens present" is useful in determining what your logical alternatives are based solely on the available authorised information. If you decide that you, and your peers, would not have considered any alternative action to call Y, had you been playing with screens, then the Laws permit to choose action Y when playing without screens, even if you have UI which could demonstrably suggest action Y.

Does the concept extend to the non offending side too ?

Example: a hand I've already posted, unopposed auction.

2♦(multi)-4♥(intended as natural, but alerted as p/c)-4♠(should be strong over a natural 4♥, but is now obviously weak)-5♥.

With screens in place, it will be obvious to the hand over 5♥ (if he's with the multier) that multier's partner has bid a p/c 4♥, then bid 5♥ which seems to make it clear a wheel has come off (and which wheel), it didn't kick off with 2N so double is close to auto with ♥Kxx pretty much regardless of the rest of the hand (in fact he has AKQxxx of clubs too).

[campboy]

 Cyberyeti, on 2011-April-06, 17:17, said:

Does the concept extend to the non offending side too ?

Example: a hand I've already posted, unopposed auction.

2♦(multi)-4♥(intended as natural, but alerted as p/c)-4♠(should be strong over a natural 4♥, but is now obviously weak)-5♥.

With screens in place, it will be obvious to the hand over 5♥ (if he's with the multier) that multier's partner has bid a p/c 4♥, then bid 5♥ which seems to make it clear a wheel has come off (and which wheel), it didn't kick off with 2N so double is close to auto with ♥Kxx pretty much regardless of the rest of the hand (in fact he has AKQxxx of clubs too).

I don't think I understand the question. Isn't all this obvious to him even without screens? He is entitled to use whatever information he gets from opponents' alerts; they are only unauthorised to each other.

[jallerton]

 Cyberyeti, on 2011-April-06, 17:17, said:

Does the concept extend to the non offending side too ?

Example: a hand I've already posted, unopposed auction.

2♦(multi)-4♥(intended as natural, but alerted as p/c)-4♠(should be strong over a natural 4♥, but is now obviously weak)-5♥.

With screens in place, it will be obvious to the hand over 5♥ (if he's with the multier) that multier's partner has bid a p/c 4♥, then bid 5♥ which seems to make it clear a wheel has come off (and which wheel), it didn't kick off with 2N so double is close to auto with ♥Kxx pretty much regardless of the rest of the hand (in fact he has AKQxxx of clubs too).

No. As far as misinformation is concerned, the TD should assume that the non-offenders receive a correct explanation of their opponents' methods (imagine that they have access to their opponents' system file).

Sometimes when playing with screens one player receives a wrong explanation from his screenmate. The screenmate may use the explanation given and is also entitled to rectification if damaged by the incorrect explanation. However, it does not follow that, when screens are not in use, East is entitled to know North's incorrect explanation of North's own bid; as long as South has explained the bid correctly, there is no misinformation.

[Cyberyeti]

 jallerton, on 2011-April-07, 00:35, said:

No. As far as misinformation is concerned, the TD should assume that the non-offenders receive a correct explanation of their opponents' methods (imagine that they have access to their opponents' system file).

Sometimes when playing with screens one player receives a wrong explanation from his screenmate. The screenmate may use the explanation given and is also entitled to rectification if damaged by the incorrect explanation. However, it does not follow that, when screens are not in use, East is entitled to know North's incorrect explanation of North's own bid; as long as South has explained the bid correctly, there is no misinformation.

The opponents disagreed what their agreement was in this case. Both were adamant they were right (insert cheap husband/wife joke here), so the introduction of an invented screen would clarify the noise to the opponents and ensure they got doubled (the appeals committee ruled not doubled much of the time).

[campboy]

Why are you adjusting in this case? The only purpose of the screens thought experiment is to decide what the LAs are, and so whether a call was an illegal use of UI. If you decide it was, and adjust on that basis, you adjust based on what might have happened if that particular irregularity had not occurred, and the hand had then proceded without further irregularity. If an incorrect explanation had been given earlier, though, since that is not the irregularity in question, NOS can still use that information to deduce that a wheel has come off.

On the other hand, if you adjust because of MI, again you adjust based on what might have happened if opponents had been correctly informed, and the hand had then proceded without further irregularity.

If you have a choice of whether to adjust for UI or for MI it is normal to pick whichever is better for NOS.