Who's at fault for Snape v. Harry?

[backstagemystic]

No: HPFGUIDX 68018

Jens wrote:
>>As for Snape's countercurse, it might well have had the effect of 
restricting the bucking of the broom somewhat. True, it wasn't enough 
and Harry would have fallen but we don't know it wasn't having any 
effect at all.<<

Yes, we do know, as Quirrel himself reveals to Harry in chapter 17 of 
PS/SS (p.289 US Hardcover):

"Another few seconds and I'd have got you off that broom.  I'd have 
managed it before then if Snape hadn't been muttering a countercurse 
trying to save you."

BM