Let's have a look at what you describe as my "hunch" concerning JFK's left arm.
It has already been established that for the full duration of the Z-film, from z133 (when we first see the presidential limo) until z225 (just after JFK emerges from behind the 'Stemmons' sign), JFK's left arm is down by his side. This is a fact, not a hunch.
Within approximately one third of a second JFK's left arm moves from this position (at z225)
To this position (at z232)
Within such a ridiculously small amount of time his left elbow goes from being down by his side at z225 to the unnaturally extended position we see in z232. This is a fact, it is not a hunch.
It would be difficult to achieve this speed of movement as a conscious action but JFK is doing it as a reflex reaction to being shot. It is reasonable to assume that prior to this moment he has no intention of raising his arm in such a fashion.
Is it a "hunch" to assume JFK is reacting to being shot?
JFK is shot through the throat. His reaction to being shot through the throat is to raise his hands up to his throat. This reaction begins at z225. This is not a hunch.
His left arm does not raise up before z225. This is not a hunch.
So if his reaction to being shot through the throat is to raise his hands to his throat, and if it can be clearly demonstrated from the Z-film that this reaction does not occur until z225 then what is this "hunch" you're talking about?
Maybe you are proposing that whilst JFK is behind the sign he has a "pre-reaction" to being shot. The problem with that is the extreme speed at which JFK moves which indicates a "reflex reaction" to being shot (NOT A GAGGING REFLEX
, A REFLEX REACTION). A Reflex Reaction would be his first response to such a traumatic injury. We don't need to guess about what's going on behind the sign as the Z-film shows us his first reaction.
So what is this "hunch"? - "That the left hand is the only indicator of whether he is reacting?"
Really? It's the
only indicator?
Are there any other extreme and rapid reactions that occur at the same time as JFK's left arm movement?
At z223 both JFK and JBC are shot through with the same bullet. The close-up of the Z-film below focusses on JBC. It begins with him looking to his right, towards the people lining Elm St. He has a quick look to his left then resumes looking to his right. By z167 JBC has completed his turn to the left and is looking towards the crowds to his right.
From this point on until he emerges from behind the Stemmons sign JBC stays in exactly this position!
The following frames from the Z-film (z222 and z223) show JBC after he has emerged from behind the sign. He shows no signs of distress and appears to look exactly the same as when he passed behind the sign:
From this seemingly relaxed position JBC undergoes a rapid and extreme reaction. He is holding his Stetson hat which is resting in his lap. Between frames z225 and z230 the Stetson suddenly leaps up to his face. This action takes approximately
one quarter of a second. It is incredibly quick. Up to this point the hat has been resting in his lap then suddenly, at exactly the same moment JFK is making his incredibly rapid movements, JBC also "decides" to make an incredibly rapid movement of his own:
But this is not the only incredibly quick movement taking place at this time. As JFK emerges from behind the sign at z224 we can see his hand is in an open position (somewhere you have used the ridiculous expression "semi clenched" but you mean "open", although not fully extended open). I have presented a clear argument that we cannot use the position of JFK's right arm/hand at this point as a reliable indicator of when JFK first reacts to being shot. The reason we can't use it as a reliable indicator is because JFK is moving it around as he passes behind the Stremmons sign.
Even so, there is still a discernable and incredibly rapid reaction that takes place which I have described as the "Hand Snap". This is a post from earlier in the thread:
JFK's reaction to being shot seems strange in a couple of ways. Firstly, he doesn't 'clutch' at his throat as one might expect, instead his hands clench into fists which he seems to jam under his chin. Secondly is the way his elbows extend upwards in quite an extreme way. For a second or so he seems to go rigid, his elbows extended upwards. To me this seems more like a reflex than a straightforward reaction to an external stimulus. The difference being that a reflex is quicker than a reaction.
The average reaction time for a visual stimulus is about 250 milliseconds. The average reaction time for an auditory stimulus is about 170 milliseconds and for a touch stimulus 150 milliseconds. [https://www.onaverage.co.uk/other-averages/average-reaction-time]
If we assume the average reaction to a touch stimulus is 150 milliseconds we can use this to get a rough estimate of when JFK was first hit. Before that, it must be established when JFK first reacted to being shot. As I stated in an earlier post, as JFK begins to emerge from behind the Stemmons sign (z224) we can see his right hand in a slightly raised position. I argued that, as he was coming to the end of his last wave I couldn't draw anything conclusive about this hand position (ie: he was already reaching for his throat) and that the movement of his left arm/hand was a much truer indication of when he reacted to being shot. It appeared to me that the most obvious reaction began at z226 but there seemed to be a hint of movement at z225. In the clip below i would like to focus on JFK's right hand. It is known that after being shot his hands clench into fists which he thrusts under his chin. The clip below shows the moment his right hand clenches shut into a fist:
It seems clear to me that his hand is beginning to close in z225 and fully closes shut in z226. From this I conclude that his very first reaction to being shot can be seen in z225.
Each Zapruder frame represents, approximately, a timespan of 55 milliseconds. If we accept the reaction time to a touch stimulus as 150 milliseconds this means the stimulus (the shot) cannot have occurred more than 4 z-frames before the reaction. That is to say, the shot to which JFK is reacting cannot have occurred before z221, particularly if it is a reflex reaction. It is also worth noting that a reflex reaction is much quicker than a normal reaction to a stimulus. As such it can be expected that the first shot hit JFK z221 to z224.
At the same moment in the Z-film there are at least three unbelievably quick reflex reactions - JFK's left elbow shooting up from his side to a point of full extension (about one third of a second), JBC's Stetson suddenly flying up from his lap close to his face (one quarter of a second) and JFK's hand snapping shut (less than one fifth of a second).
Three extremely rapid reactions, all occurring at the same time. To postulate these are reactions to stimulus a couple of seconds earlier is absurd.