The driver shot JFK clearly and obviously but the zapruder film needed to be picked apart and analyzed by someone and that someone turned out to be me.
Nix film close-up shows Greer's left arm crossing over.
I got this gif from this clip. Start it at 1:09 and see Greer quickly moving his left arm over his shoulder in unison with the headshot. The nix film was not shown close-up but when this sequence is zoomed in on the limo, this whopper is revealed. The goons covered those movements with fakery in the zfilm but could not or didn't bother with the nix film.
THE FAKE GREY STREAK covered Greer's arm movement in the zfilm and the nix film proves that alteration beyond any doubt. Case Closed, finally.
The driver killed Kennedy and the Nix film provides conclusive proof to this inevitable truth.