Simultaneous Spell Casting (was Re: Snape didn't kill DD with AK!! And here's the evidence...)

[houyhnhnm102]

No: HPFGUIDX 138734

CathyD now:
[...]
> It is interesting to note that Expelliarmus, which usually 
> simply disarms  the other person, acted very strangely 
> when Snape used it on Lockhart in Duelling Club: "Both of 
> them swung their wands up and over their  
> shoulders. Snape cried: 'Expelliarmus!' There 
> was a dazzling flash  of scarlet light and Lockhart 
> was blasted off his feet: he flew backwards 
> off the stage, smashed into the wall and slid 
> down it to sprawl on the floor." (CoS pg 142 Can Ed) 
> Extra powerful Expelliarmus or an extra spell? Only 
> JKR knows for sure! ;-)

houyhnhnm:

Aren't there some other occasions in which a spell blasts someone off 
their feet?  I have been wondering lately if the "three Ds" aren't 
important in all kinds of magic, not just apparition.

In the case of a charm, the person or object being charmed would be 
the Destination.  Determination would be the intent to produce a 
particular effect.  Deliberation would be the mental efficiency with 
which the spell was cast.

A spell cast with insufficient Determination would simply fail to 
produce its intended effect.  One cast with insufficient Deliberation 
would produce the effect, but also produce an excess of unfocused 
energy, resulting in a blast.

Could this be what happened on the tower?  Snape lacked the 
Determination to kill Dumbledore, resulting in a failed AK.  Being in 
a state of extreme emotional distress, he also lacked Deliberation, 
resulting in a blast.  I still can't figure out the upwards part, 
though.  How high were the battlements?  How far down had Dumbledore 
slipped?  It does seem that Snape's wand would have been pointing 
downwards.  Maybe the wall wasn't very high (and Dumbledore was a 
*tall* man.)  I think the fact that Dumbledore seemed to hang in mid-
air and fall slowly was just the way Harry saw it, the way people 
experience extremely traumatic events as if they took place in slow 
motion.