We have seen film proof that both JFK and JBC are making extremely rapid movements just as they emerge from behind the Stemmons sign [Reply#1087, page 136].
Scientific proof had been presented that a detectable reflex reaction can occur within 2 Z-frames [Reply#1103]
What frame does JBC first show signs of reacting?
It seems clear, to me at least, that JBC is showing no signs of a physical reaction in z223, the picture below.
This appears to be the same position and posture he has before he passes behind the Stemmons sign.
After this frame JBC's physical appearance and appearance begin to rapidly change:
In 1976 the Itek Corporation, specialists in photographic analysis, looked at the issue of exactly when Connally was showing a reaction to being hit. The following is their report.
By frame 232-234 there is strong evidence that the Governor is reacting to a significant effect on his body; or from other data, to a bullet wound. He placed the time of his reaction at 234. We studied the film in this area to determine if there were any striking changes in his physical appearance which could be interpreted as the onset of a reaction. Five photo analysts studied the original film from frames 222-240. They all concluded independently that somewhere between 223-226 there are signs of the beginning of a significant change in the governor's position and appearance. Some of their comments are paraphrased below.
— As Connally first clears the obscuring sign on frame 221, his facial features are not discernable or distinct. Frames 222 and 223 show no unusual action and Connally's face and features remain frozen (normal). With frame 224, I observe a slight grimace, a minor body twist, a slight arching of the back and a rearward head motion. These reactions continue on frame 225 which includes a slight hiking up in the seat. By frame 226 Connally's head is turned forward which I judged to be a rapid reaction. Frame 227 yields no information due to the high amount of smear, but the following frames 228, 9 and 30 indicate a rapid reaction of the hand holding the Stetson which was flicked up and down quickly.
— I observe a rotation of the Governor's body from right to left beginning at frame 223. It isn't obvious that this is significant relative to the study objective, however I also observe what I would consider an involuntary and unusual motion of his right hand and arm at 225. Before 225, his hand is hidden from Zapruder's view, down below the edge of the door. At 225-226 it can be seen to travel rapidly upward until it is about level with his chin in 228. From 228-230 he flips his hat rapidly. At 229 it appears upside down in his hand with the thin edge of the brim extending toward Zapruder. By 230 the hat has flipped so that one can now see into it. This all takes place within less than 1/3 of a second so it would appear to be somewhat unusual.
— At frame #223 he is turned in the jump seat sitting well into the car. I noticed a facial expression changing between #223 and 224 to a grimacing look. His body has moved forward (toward the edge of the car) with his right shoulder twisting to his left and downward. Between frames #225 and 226 a rapid motion of the Governor's right hand begins, i.e. #225 - his hand inside of car, #226 - his Stetson hat appears over the edge of the car, #228 - the hat is up in front of his chin concealing it. At #229 and 230 he flips his hat from edge on to a view of looking at the inside of it.
Source: "John Kennedy Assassination Film Analysis" — Itek Corporation, May 2, 1976, pp. 36-39 Emphasis in original.
(https://mcadams.posc.mu.edu/jbchit.htm)From z223 to z224 certain changes are noticeable, including a slight rotation or twist in JBC's upright position, his right shoulder moving slightly forward and downward and his left shoulder moving slightly upward and backwards.
It is also noticeable that there is a radical bulging of the right side of JBC's suit jacket between the 2 frames. The same side the bullet exits through:
This is the moment JBC's extremely rapid movement begins, from a resting, relaxed position, resulting in his Stetson being raised up to his face from down by his side in one third of a second.
The Zapruder film reveals when JFK begins his extreme and rapid reaction.
As he emerges from behind the Stemmons sign his LEFT ARM is down by his side. It is down by his side as he passes behind the Stemmons sign. The pic below shows his LEFT ARM down by his side in z193 [the last clear frame before he passes behind the Stemmons sign] alongside z224, the first clear frame of JFK as he emerges from behind the Stemmons sign.
From being down at his side, JFK's LEFT ARM suddenly rockets upwards. It is an incredibly rapid movement. The gif below shows the beginning of this incredibly rapid movement:
z224 shows the left arm down by the side. The left elbow is hidden below the edge of the door.
z225 shows a slight movement of the left arm but the left elbow is still below the edge of the door.
z226 shows the left arm is definitely beginning to rise as the left elbow comes above the edge of the door.
From being down by his side in z224, JFK's LEFT ARM shoots up to this extreme position in z232
This movement occurs in 0.44 seconds. It is an extreme and rapid reaction that begins at z225.
The Z-film proves both men had extreme and rapid reactions beginning at the same moment from a resting position.