For the first time and only today, we finally hear first-hand the defence. The firing of four shots was an involuntary reflex in response to the noise.
Roux said it was a startle/exaggerated startle/exaggerated fight and it was supported by expert evidence of Derman and Scholtz.
This was not the evidence of these witnesses however. Nowhere did they ever claim the firing was involuntary, and they in fact contradicted it (Scholz found OP was able to act in accordance with right or wrong, ie voluntarily, and Derman said you had to ask OP why he fired not him).
There is gross misrepresentation also of what a startle response is. It is a very brief, involuntary, bilateral and symmetrical (both sides of body at same time) reflex. It's components can include a blink, a flinch and stiffening of the neck or shoulder muscles, or a whole-body response of both arms, legs and torso - in humans the latter is a primitive reflex of new borns that disappears. It is observed in rodents, mammals, birds, fish. The studies Derman talked about, electrodes measure the tiny variation in duration and intensity of blinks - this is the measured exaggerated startle in research. A startle response can never, ever comprise the firing of a gun - this is simple fact of the science. Although he did not (deliberately?) make it clear, Derman did in the end define startle response as a blink or contraction of neck/shoulder/back muscles (I can't remember exactly - I hope to find that portion).
A startle response commonly leads to a stress or neuro endocrine/adrenaline response (various names inc fight or flight). The physiological changes of the body are indeed involuntary. But the behavioural positive actions are voluntary (as we know from our own experience). They are not a reflex. Therefore, still - the firing of a gun cannot (and has not) be said to be, scientifically and from an expert viewpoint, an involuntary reflex.
In the UK, if a doctor allowed expert evidence to be used in this way, he would certainly face a hearing with a view to be struck off.
Nel began yesterday with brilliant points. OPs own evidence of thinking what the sound was and meant- after the noise before firing - and that this thought not the noise caused him to fire - makes the defence impossible.
His further point about sitting on 2 chairs at once - wanting the mutually exclusive defence of putative self defence as a backup was also spot on.