Snape warned James?

[aggiepaddy]

No: HPFGUIDX 106587

I tried the search engine to see if this had been discussed before 
but couldn't find it. I'm sure it has but hey-ho, off we go. . .! ;o)

Having just read the Shreiking Shack scene in PoA again for the 
umpteenth time (it's one of my faves!) I noticed something that 
hadn't registered before.

When Snape is shouting at Harry he says (Ch19 uk p265) '...You'd have 
died like your father, too arrogant *to believe* you might be 
mistaken in Black -...'   (emphasis mine)

To me it seems that Snape KNEW James had been warned about BLACK.  
You can't *not believe* something you don't know!  As it appears that 
no-one 'knew' Black was the traitor before GH happened, it strikes me 
that what Snape says here is weird.  

I am now wondering if Peter, who had been spying for LV for a year 
before GH (PoA uk p274 ch19), told LV that Black was going to be 
secret keeper but that he (Peter) would try to manipulate Black to 
change.  LV could have used this info to flush out his traitor. If he 
suspected Snape, he could have told him that Black was going to turn 
on James.  Snape then informs DD or tells James himself to watch out 
for Black.  James doesn't believe him and, as far as Snape knows, 
keeps the secret keeper as Black.  This would infuriate Snape no end 
and would go part way to explain his actions in the SS.  LV would 
then know that Snape was the traitor as it would get back to him that 
Black was suspected. 

What do you think?

"aggiepaddy"