The logic is simple:
1. Seven frames are missing (spliced out) from the Tina Towner film.
2. The Towners did not remove them.
3. Other than the Towners, the FBI were the only ones in possession of the film.
4. The FBI were the only ones who could have possibly removed these seven frames.
5. The FBI removed these seven frames.
6. These seven frames reveal a major camera jiggle. (See below.)
7. This camera jiggle is Tina Towner’s reaction to the first shot.
8. This camera jiggle occurs as the limousine is making the turn onto Elm Street.
9. Most career-trained witnesses said that the first shot occurred as the limousine was making the turn onto Elm Street or in the process of completing its turn.
10. The detailed jiggle analysis in The Final Truth demonstrates that Tina Towner would have reacted exactly at the first missing frame.
Conclusion: The first shot was fired as the limousine was making the turn onto Elm Street immediately prior to the seven-frame jiggle splice in the Tina Towner film.
Note the sharp upward movement during the missing frames, a radical aberration from her otherwise smooth-as-glass pan. Added yellow lines help show this sharp rapid movement within 0.307 of a second (the Towner’s camera filmed at 22.8 frames per second). The splice is between T084 and T085. This video uses retouched versions of these frames not obscured by splicing cement.
Detailed description in The Final Truth: Solving the Mystery of the JFK Assassination.