OK, Yellowjacket, I'll explain again.
There are two completely distinct concepts in criminal law operating here. There is the verdict of a jury -- a finding of fact -- which is guilty or not guilty. And then there is the actual fact of guilt or innocence.
Suppose, for example, that you murder your professor in cold blood and with malice aforethought. Suppose also that you are never discovered. Then you are never convicted ("found guilty") of murder, but you ARE guilty of murder. (This would remain true if you were tried and acquitted).
On the other hand, suppose you do NOT rob your student's house, but you are accused of it and convicted. Then you are innocent of robbery, yet you are convicted ("found guilty") of it. Without this distinction, criminal law would not make any sense. For example, it would make no sense to say a jury made a mistake in convicting somebody if there were no actual "matter of fact" that they were supposed to be finding. We can talk of mistake precisely because there is an underlying truth -- somebody is guilty or innocent. On the other hand, a mistake in acquitting somebody is more subtle; it may be the *right* verdict to acquit somebody (find them "not guilty") somebody who is actually guilty, because the evidence was insufficient.
Notice, therefore, that I'm using "innocent" and "not guilty" to refer to different things. Innocence is a question of actual fact -- you really did or did not commit the crime. "Not guilty" is the finding of a jury as to whether there is sufficient evidence to convict you of the crime (evidence of guilt beyond a reasonable doubt).
So when I said above you were *innocent* of robbing your student's house, innocent was precisely the right word to use. Also, contra your assertion, it IS a legal term. This, like the verdict of a jury, is a LEGAL concept. Somebody is innocent of a crime precisely if they have not committed the crime, and the crime is legally defined, with elements that must be met for it to have occurred. This is completely distinct from any question of a court, trial, or jury. You can be guilty of many crimes without anybody else ever suspecting or even thinking of charging you. If you drive at 90 mph with nobody around, you are still not innocent of speeding, though you will likely never be charged.
When talking about a trial, what the jury is doing is starting with a presumption that the person is innocent, and then considering whether there is sufficient proof (beyond a reasonable doubt) of each element of the crime that that presumption is overturned and they can decide they are guilty. Again, if they acquit, this is distinct from saying there is evidence that they are innocent.
As with the experimentalist who measures the position of a macroscopic particle, there is an actual position (guilt/innocence), and a measured position (guilty/not guilty). We want the two to be the same, but they are certainly distinct concepts, and it is not useful to conflate them by using the same terms. It is unfortunate in some sense that "guilty" is one side of both dijunctions. It is useful to distinguish guilt from conviction, therefore.
My first point then, can be rephrased: if there is a reasonable doubt that the person is (actually) guilty, i.e., a reasonable possibility that he is (actually) innocent, THEN an acquital, i.e., a verdict of not guilty, is required.
If one conflates the concepts of acquittal and innocence here, the whole thing becomes meaningless. Until the jury returns "guilty" or "not guilty," there IS no verdict; but there ARE facts (actual guilt/innocence) to consider and attempt to discern, and it is on these that the jury returns its verdict.
My argument was therefore exactly correct, and phrased as precisely as possible. If somebody kills in self-defense, he is ACTUALLY innocent. This is a legal concept, albeit not a verdict.
Therefore, if there is a reasonable possibility that somebody killed in self defense, then there is a reasonable possibility that he is actually innocent, and therefore, the jury is required to FIND him "Not Guilty." This is a straightforward classical syllogism. I can't make it any clearer.
The above analysis would only be muddied if "not guilty" were substituted for "innocent," since actual innocence and a verdict are completely distinct legal concepts, and a jury is supposed to consider one while creating the other. (It would create the risk of a tautology to say that somebody is not guilty if there is a possibility that he is not guilty).
I have answered at some length in the hopes that you may understand, since short and straightforward explanations were apparently evading you.