In the book Reasonable Doubt, by Henry Hurt, he based the shooting on the Zapruder film, and it is largely agreed that all the shooting occurred within a span of 5.6 seconds. He explained how master marksmen (the highest rifle-expert rating of the National Rifle Association) and top FBI agents, tried to match this firing time with Oswald's rifle in shooting tests. The rickety rifle had been examined thoroughly, but experts found that getting three shots was extremely difficult even for them. Even the shots they could fire in that time span did not match Oswald's supposed superlative accuracy. Hurt concluded that if expert marksmen cannot shoot at this level, how did a marine who was a poor marksman do it? The answer he said was very simple, Oswald was not alone in the shooting, maybe Oswald did not even shoot. .
The rifle Oswald had was a cheap mail order rifle purchased in March 1963. The gun later examined by FBI was a Mannlicher-Carcano. It had a defective scope and needed great skill of the shooter to compensate for the error. Those skills were the ones Oswald did not have. It seems practically impossible for Oswald for to have shot at such accuracy. .
On the day of Lee Harvey Oswald's arrest, the Dallas police gave him a "nitrate" test. The test is designed to reveal any deposits of nitrate (from gunpowder) on the suspect's skin. According to the Dallas Police Oswald's hand and his right cheek were tested, but only his hand showed positive reactions to the test but not his cheeks. This means that Oswald did not fire a rifle as if he did he would have had nitrate deposits on his cheeks as well. This evidence concludes that Oswald did not even fire the rifle. .
The shooting of Kennedy in the neck is impossible from such an angle from the 6th floor of the book depository. From this angle it is almost impossible to shoot at the neck, as the head would be covering in. From that angle of the bullet would not go straight through the throat but continue a downward path following the direction of where the bullet came from.