How did DD know that Fake!Moody was Barty Jr.? (Was: Hogwarts House-elves )

[justcarol67]

No: HPFGUIDX 161851

PforParvati wrote:

> > Hi..I have one doubt here. How did Dumbledore know in advance that
Winky would be needed there? I mean Dumbledore realised that it was a
fake Moody. But how did he relate it to Crouch & Winky before 
polyjuice potion wearing off.
> 
Pippin responded:
> Sirius is probably the missing link here. He knew that Harry had
seen Bartemius Crouch on the Map, burgling Snape's office. We also
know that Sirius was in contact with Dumbledore (quoting from memory,
> "You are not Sirius's only correspondent.") 

Carol adds:
Also, Dumbledore had been studying memories related to the various
people who could have put Harry's name in the Goblet of Fire,
including Barty Crouch Sr. He would also be thinking about Barty Sr.'s
disappearance, and he would know from Snape that Polyjuice ingredients
had been stolen from his supplies. So when Fake!Moody disobeyed him
and ran off with Harry, everything would come together in his mind. He
would know who the Death Eater impersonating Moody had to be, even
though Barty Jr. was presumed dead. And if, as Pippin suggests, DD
knew from SB that Bartemius Crouch had been burgling Snape's office,
that would mean that Bartemius Crouch was the impersonator. But it
couldn't be Barty Sr., who was dead, and who had been seen in the same
place at the same time as Fake!Moody, ergo it had to be Barty Jr.

Here's a link to an old post of mine on the topic if you're interested:

http://groups.yahoo.com/group/HPforGrownups/message/123284

Carol, wondering how Harry can consider the possibility that DD is "a
foolish old man" (HBP) after a deduction of this magnitude