Snape's involvement in the murder of Sirius

[justcarol67]

No: HPFGUIDX 169148

Carol earlier:
> 
> The only problem is, there is no such plot in canon. The only plot
is to get Harry to the MoM using a fake Sirius (a phony vision) as a
> decoy. <snip>

> 1) There is no plot in canon to kill Sirius Black, only to get
*Harry* to the MoM.
> 
> 2) There is no reason to kill Black, who is stuck in 12 GP and no
> threat to the DEs or Voldemort.
> 
> 3) Snape canonically did everything he could to keep Black from
coming to the MoM (it was Black's own decision to come). <snip>
> 
> 4) There was no guarantee that Black would be killed if he did come.
Had he not been fighting recklessly on the dais in front of the Veil,
he could not have been sent through it.
> 
> 5) Snape certainly gave *some* information regarding Black, probably
that he had seen him in Animagus form at Hogwarts just before his 
return, and he no doubt used that bit of information to claim a share
in Black's death, but it really made no contribution to Black's death
at all.
<snip>

Carol again:

My apologies for adding to my own post, but I forgot to mention that
any information that Snape could have provided on Black (that he'd
seen him at Hogwarts in Animagus form, that he was hiding out at Order
HQ [whose address he couldn't give because of the Fidelius Charm]) had
no actual bearing on Black's death.

The guilty parties were Bellatrix, who actually killed him; and
Voldemort, the Malfoys, and Kreacher, who together set up and/or acted
out the plot to get *Harry* to the MoM.

In terms of *unintended* consequences, Harry is partially and
accidentally responsible--not for Black's death per se but for going
to the MoM in the first place--with the best of intentions, of course,
but he should have listened to Hermione. Had he not fallen for the
fake vision and gone to the MoM, Black would still be safely at 12 GP.
(Harry would also have been responsible to some degree had any of his
friends been killed, and he knows it.) 

Black, too, bears some unintended responsibility for his own death. He
could not have been killed had he not chosen to ignore Snape and go to
the MoM to save Harry--again, perfectly laudable. But he was also
careless, laughing and taunting Cousin Bellatrix instead of paying
attention to where he was, standing with his back to the Veil. As much
as anything, it was Black's own reckless courage that killed him. Or
perhaps he didn't know what the Veil was though that seems unlikely.
Based on her triumphant scream, Bellatrix knew, so why wouldn't her
cousin, "the Animagus Black"?

Carol, noting again that nothing Snape could have told Voldemort made
any real contribution to Black's death; Black was there *in spite of*
Snape's warning (so far as we know), and his death was in no way
inevitable even after he arrived