[blml] "Demonstrably" - practical meaning?

[Guthrie]

[Eric Landau]
I like the "opposite adjustment" test.  A player with UI has 
successfully chosen action A over action B, and you must decide
whether A was "demonstrably suggested over" B.  Imagine that the same
player, with the same table action, had chosen B, and that the deal
was such that B turned out to be the winning decision rather than A.
Would you consider adjusting the score under those circumstances?  If
you would, you should not adjust now (or then). IMO this appropriately 
reflects the apparent intention of the authors who, in 1997, carefully 
changed the key word in L16A from "reasonably" to "demonstrably".

[Jerry Fusselman]
Oh, I agree!  The opposite-adjustment test is magnificent.  It would
have prevented dozens of errors that appear in the ACBL casebooks.  I
think that failure to apply the opposite-adjustment test is one of the
easiest ways for the director or committee or panel to err.

[Nige1]
Eric's proposal is similar to (but slightly less objective than) what I 
suggest: that a panel of the player's peers should decide
  - what are the logical alternatives.
  - what action was suggested by the unauthorised information.
both of these *without knowing* what action was in fact chosen and the 
actual result.

Such assessments are unlikely to be unanimous. Hence to be practical, 
such protocols depend on probabilistic criteria. They're certainly not 
"provable". But are they what Bridge law means by "demonstrable"?