No, I'm not wrong and I didn't use "immediately" either. Now in the part you quoted he was addressing that specific qualifier in his answer to Wilmott's use of "completely" and "immediately" in her questions, IMO. He is an MD, he's hearing specific terms, and those words mean different things medically. "Completely" would mean unconscious. In this statement he is referring to earlier testimony where at one point he did concede that although he believes TA would have been unconscious, he can't be absolutely certain of that and it might have taken seconds for incapacitation. But he added that TA wouldn't have been capable of purposeful movement even if conscious for a short period of time. In the clarification that follows your snippet, he uses simply incapacitation because he did make that one earlier concession. IMO
But OK, lets ignore hours of testimony about his certainty of incapacitation (whether immediate or not), both injuries to the skull, damage to the brain, and zoom in on this one fragment of a sentence as you prefer. First of all, there is no break in his speech pattern that indicates anything or anyone caused him to change a thing and you dont know who he glanced at it was more likely Flores IMO. You want to use it, so you interpret a quick glance as being intimidated into changing testimony, and quote just a snippet for proof of your theory? He looks in several directions throughout his days on the stand, including this section, just as most witnesses do At times he glances down, to his left, his right and even to the direction of the defense team, so does that mean hes taking direction from them or the court reporter too?
Next, lets look at the whole statement, not just part of it (or better, watch it @ beginning about 2:41:00
https://www.youtube.com/watch?feature=player_detailpage&v=1tZKYBlfkxI#t=7750s . In the part you quoted he does glance in (IMO)Flores direction but does several times, even before saying what you want to use and claim he changed. Maybe because Flores is the subject? Doesnt appear to me that hes influenced at all by anything other than his own expert medical opinion of the facts. Heres the transcript that includes your snippet:
Jennifer Willmott: And, do you remember telling Detective Flores that you knew this because the gunshot wound wouldn't have completely incapacitated somebody?
Kevin Horn: I don't recall saying that either.
Jennifer Willmott: Is that something that you think you would have never said to Detective Flores?
Kevin Horn: I think I've said it in court that I don't think it would immediately incapacitate or kill him, but it would be a serious injury. But I don't recall telling Detective Flores that, no.
Jennifer Willmott: Okay. So, let me back up for a second. So you're saying that the gunshot wound is not immediately incapacitating.
Kevin Horn: I would say not immediately fatal.
Jennifer Willmott: Okay. I'm not talking about fatal, I'm just talking about incapacitating.
Kevin Horn: I think, yes. I think that it would be incapacitating. It's passing through his brain, so yes.
Jennifer Willmott: Okay. So... And that's assuming it passed through his brain, you would say it's incapacitating, right?
Kevin Horn: I'm saying it did pass through his brain.
And now that youre willing to again discuss Horn's testimony, maybe youll finally answer my repeated question. How does a bullet exit the cranial cavity, leaving a large hole in the plate, if it was never there to begin with?