Instead of examining the autopsy X-rays and photographs,
the Warren Commission introduced into evidence a drawing
that did not accurately depict the President's wounds.
The Zapruder film contradicts the Warren Commission
drawing of the President's head wounds. The drawing
has Kennedy leaning forward in the wrong position
so the path of the bullet through the head wounds
descends from back to front, consistent with a
shot from the Book Depository Building.
When the drawing is turned so Kennedy is in the position
seen in frame 312 of the Zapruder film (the frame
before the fatal shot), the path of the bullet rises
from back to front, which is inconsistent with a
shot fired from the Book Depository.
Defenders of the lone assassin theory are confronted
with a classic dilemma known as Warren's Dilemma:
If the Warren Commission drawing accurately represents
the President's head wounds, then the Zapruder film
was altered, hence conspiracy, hence cover-up. If
the Zapruder film is authentic, then the Warren Commission
drawing is a false representation of the President's
head wounds, hence conspiracy, hence cover-up.