Does LV know Snape is at Hogwarts?

[soccerboyatut2004]

No: HPFGUIDX 95979

Voldy (in Quirrel) was at Hogwarts with Snape (not too quick are you 
DD?).  He heard Snape threaten Quirrel about the stone.  LV knows 
Snape is a traitor, right?  

So Snape is the death eater who "one is a traitor, and certainly will 
die"-LV in GoF.  Right?

Bet he dies protecting Harry, fulfilling the debt to James.

Whatcha think?
-strongbad