MR LAX
Sorry, before you do and while we are on this issue, if I might interpose Chair?  I'm a bit puzzled by this myself and I've heard all the answers that have been given so far to this issue and the only basis I would understand that you might expose the informer is if the informer was one of those people in the house who would be arrested with you.  Any other basis that would exclude that, how would you possibly expose such an informer?