Why did Jim garrison say back and to the left?

Jim Garrison, the New Orleans District Attorney, used the phrase "back and to the left" to describe the motion of President John F. Kennedy's head during the assassination in Dallas on November 22, 1963. This statement was part of Garrison's argument that the trajectory of the fatal shot indicated it came from the front rather than from behind, challenging the official narrative that Lee Harvey Oswald acted alone. The phrase became iconic, particularly due to its use in the documentary "JFK" by Oliver Stone, highlighting the controversy and conspiracy theories surrounding the assassination.