It all depends upon the jury, and the attornies I'm thinking.
Actually, should it go that far, it depends on the law, the evidence presented by you and by the state including witness testimony, the jury instructions, and on the jury and the attorneys.
If the witnesses testify (and/or for that matter, the forensic evidence indicates) that, upon your presentation of a weapon, the attacker made it clear that he was no longer interested in harming you
and you shot anyway, your defense is going to have to depend entirely upon a discussion of reaction time and the details of the evidence and testimony as they relate to timing. If the net result is that the jury believes that you could not have stopped what started out as a justified shot in time, you will be OK; otherwise no. That phraseology probably needs work for accuracy to take into account burden of proof, but the idea should be clear enough.
You may prevail, and you may not.
As Fiddletown pointed out in Post 42,
Mas, IIRC, was involved in at least one case in which the defender fired late, as the assailant was breaking off the attack. The defense was able to prevail by putting on expert testimony about reaction times and the time lag involved in trying to stop and reverse an action in progress. But whenever a legal defense needs to be based on that sort of reasonably esoteric information, there's a risk that a jury won't be able to process the concepts.
Not a good time to have trained oneself to shoot automatically, for those who have for some reason done so.
My experience has been limited to indoor situations, and while I've never had to fire I've never had to draw from concealment.
If one believes that he will fire 99% percent of the time if he draws, and if real experience indicates that the mere presentation of a weapon resolves conflicts in 95% of the instances, one is either (1) expecting to always encounter a very rare kind of violent attacker, (2) expecting to stretch his defense of justifiability to or beyond the limit at great risk to the outcome, (3) waiting too long to draw at great risk to his own safety, or (4) some combination of the foregoing.
It's a dilemma for anyone. If evasion and avoidance don't work in the face of a serious imminent threat, one may have to draw a deadly weapon. I believe it is incumbent upon oneself to be able to do so very quickly, to err on the side of sooner rather than later (in some states, including Texas, that's provided for in the law), and to be well trained to avoid shooting too late.
Again, back to Fiddletown in Post 42:
On the other hand, if you draw your gun and don't fire, at least no one has been shot. At worst someone has been scared. So, with no blood on the sidewalk and no holes in any protoplasm, you'll probably be okay if you can do a decent job of articulating why (1) in the same situation a reasonable and prudent person would have concluded that lethal force was necessary to prevent otherwise unavoidable, immediate death or grave bodily injury to an innocent; (2) you reasonably determined it was necessary to draw your gun to defend yourseld, or an innocent third party; and (3) the situation changed so that there was no longer a reason to shoot.
All things considered, the latter should be a much easier sell than trying to explain why you used high speed lead projectiles to punch holes in the living flesh of someone who had given up or otherwise was no longer a threat.