Just before opening ceremonies began, you noticed a port bottle sitting out in the common area for the con. You had heard that there was going to be some kind of toast during opening ceremonies, and figured that this bottle was probably supposed to be involved in that. (Certainly it shouldn't be just sitting out there -- after the discussion last week about minors, alcohol, and liability, you are a bit conscious of the issue.) So you brought it into the Plymouth room, put it down with the other similar bottles, and thought no more about it.
But now Jeff is dead, apparently poisoned by a drink from one of those port bottles, and you are getting very worried that it was the one you put there. But if that's so, why would a poisoned port bottle have been sitting in the common area in the first place?