In this printscreen of the Bell footage
we can see the top say 30 inches of Officer Murphy standing on the eastern side of the Stemmons overpass.
Our view of him is mostly blocked by the overhead signs.
The JFK limo will pass under him in about 10 sec as it enters the Stemmons on-ramp.We know its Murphy koz that dark lump duznt appear in early frames, & is seen in later frames.
Murphy appears to be very high up. I am fairly certain that there aint any high curb for him to stand on.
I suspect that he heard the shooting & sirens &
he stood high up on his 3-wheeler (did he have a 3-wheeler) to see over the signage.
Murphy heard Oswald's shot-1 at 0.8 sec after Z113, then Oswald's shot-2 5.7 sec later at Z218, then Hickey's shots-123456 5.0 sec later at Z313.
It calculates to 5.2 sec but i had to deduct 0.2 sec koz of the diff in travel times for the sound of shots by Oswald who is further away than Hickey.
Murphy wasn't visible in Bell's footage when JFK's limo was half in shade entering the triple underpass at Z468.
And then Murphy was fully up & visible at Z470 when the limo was 3/4 in shade.
Z313 to Z468 is 55 frames ie 3.0 sec, hence Murphy reacted to the final shots in 2.5 sec (allowing 0.5 sec for the speed of sound).
Yes, Murphy didnt react to Óswald's shots, but Hickey's auto burst finally did the trick.
We can see say 2.5 ft of Murphy over the signage, & the signage is 61 yd away from him, which is 1/5th
of the distance to Bell (308 yd), hence that 2.5 ft gains him say 12.5 ft of extra vertical vision at Bell, but Bell is standing in the peristyle, or in the garden bed in front of the peristyle,
& that 12.5 ft has to be measured down from the level of Bell's camera.
And anyhow Murphy's vision of Dealey Plaza is blocked by the concrete eastern barrier of the triple underpass which is 23 ft high.
Actually, Murphy could see much of Elm St to the left of the signage, but he couldn't see JFK or Hickey in the middle of Elm St at Z313 koz the paling fence
was on his sight-line, plus there are 3 trees on the grassy knoll.
But praps Murphy could see a bit of JFK & Co later further down Elm St, & he climbed onto his 3-wheeler (did he have a 3-wheeler) for a better look.
I reckon that he had a 3-wheeler. Its elementary.
Actually, Robin Unger's gallery of Bell's footage has 56/208 which shows Murphy high up over the signage.
Later, i show that one of Robin's frames shows that later Murphy moves to the western barrier after JFK & Co have passed.