Patronuses and Proof

[pippin_999]

> Potioncat:
> But we're told Dark Magic can't be used on them and they can't be 
> counterfitted....so it would seem that if Snape's Patronus showed
up, 
> it would be recognised. Would it be proof that Snape was a good
guy, or 
> seen as proof that he is a powerful Dark Wizard who can manipulate 
> Patronuses?

Pippin:
There are two facts to consider:

1) Snape's patronus would give too much away.
2) Dumbledore knows what it is.

I don't see how we can possibly reconcile that with Badguy!Snape, 
unless the patronus would give away an animagus form or something
like that.

Pippin