Spies, Lies and Self fullfilling prophecies

[justcarol67]

No: HPFGUIDX 146319

kchuplis wrote (asking the same question that arose in my mind as I
read Pippin's post):
> > OK, here is where I get confused....where do Snape and Sirius say
they suspected Lupin of aiding Death Eaters?

Pippin supplied these quotes from PoA as canon support:
> [Snape:]"It seems --almost impossible--that Black could have entered
the school without inside help. I did express my concerns when you
appointed--"

and

> "Not if he thought I was the spy, Peter," said Lupin. "I assume
that's why you didn't tell me, Sirius?" he said casually over
Pettigrew's head.
> 
> "Forgive me, Remus," said Black.
> -- PoA ch 19

Carol responds:
What the Snape quote illustrates, IMO, is simply Snape's belief
(repeated in the Shrieking Shack) that Lupin is helping Black get into
the school. He believes (understandably) that Black tried to murder
him when they were both sixteen, and like everyone else in the WW,
that Black murdered Pettigrew and twelve Muggles. Black has succeeded
in getting into the school, slashing up the Fat Lady's portrait like a
"murderous, raving lunatic" (to quote movie!Ron). Snape, not knowing
about the map or Black's ability to transform, concludes that someone
must be helping Black get into the school and that the obvious person
to do so is Lupin, who in Snape's view is putting old friendships
above the safety of the students, and Harry in particular, by trying
to smuggle a murderer into the school. 

But there's no indication from Snape's words that he believes Lupin
was the spy who betrayed the Potters. It seems much more likely that
he believes that the spy was the supposed murderer Sirius Black. Snape
even seems to have tried somehow to warn James Potter against Black,
but Potter was "too arrogant" to believe him. So, IMO, the only
supposed DE that Snape thinks Lupin is helping is the "murderin'
traitor" Black (to use Hagrid's words). 

By HBP, of course, Snape knows that the traitor/murderer was
Pettigrew, whom he treats with contempt and labels as "vermin." But
there's no indication that he holds Lupin in similar contempt, however
much he still dislikes him.

The Lupin/Black exchange, IMO, simply shows that each thought the
other was a spy. Each knew that someone close to the Potters was the
spy; each knew that he himself was not the spy; each underestimated
Peter Pettigrew. That leaves only one suspect apiece: Lupin suspected
Black and Black suspected Lupin. One had the Black family history to
go on as "evidence"; the other had the alliance of many werewolves
with Voldemort to support his suspicions. If PP was the spy, as canon
so far clearly indicates, he would have played one against the other,
meanwhile making himself look like the Potters' most loyal friend
(note the photo of the old Order where he's sitting between James and
Lily). He would not have needed to listen at doorways to be a spy.
Everything he needed to hear would have been spoken in his hearing on
the assumption that he was a loyal friend and a worshipper of James.

Carol, who does see the little plot hole involving Bertha but thinks
it's only an oversight on JKR's part, not evidence for ESE!Lupin