What is with the "Prank" ?

[pippin_999]

No: HPFGUIDX 99534

--- In HPforGrownups at yahoogroups.com, sunnylove0 at a... 
wrote:

> But why would he have fallen for Sirius's bait if he knew?  
>Well....
<snip interesting theory>

If Snape wanted to kill himself, surely he'd use a potion instead. 
And how, in your scenario, would James or Lupin have been 
implicated? 

Not that it refutes your theory but there's another possibility/ 
Snape could have been under the Imperius curse. He might not 
know what had happened to him...students weren't usually 
taught how it feels. If  the curse was lifted by the shock of seeing 
the werewolf, no one would know why Snape had gone into the 
tunnel.

That would, of course, make it murder. I don't believe Sirius was 
capable of that, whatever Snape thinks. I can see Sirius killing 
somebody in a passion, but not in cold blood. But 
EverSoEvil!Lupin ...

As long as Snape was watching the willow there couldn't be any 
more marauder escapades. That gives Lupin a stronger  motive 
than Sirius.

 It would have been easy for Lupin to suggest to Sirius that it 
would serve Snape right if he *did* find out where Lupin went 
every month.  It would have been easy for Dumbledore to believe 
that Snape had found his way into the willow on his own, given 
his propensity for spying. 

  Dumbledore would not consider  Lupin guilty for  the 
werewolf's deed. All it needed was for Sirius to keep quiet, and 
James not to interfere, and the whole thing could have been 
hushed up as a tragic accident, or a blunder of Snape's.

Pippin