Many believe there was a conspiracy because:
* The shooting of President Kennedy was beyond the capability of any one man to perform, and therefore there must have been more than one gunman. They point out that no rifleman in any of the assassination simulations has scored two hits in three shots in 6-9 seconds against a moving target from a 60-foot elevation on the first attempt, which is what Oswald allegedly did. They also note that nearly everyone who saw Oswald fire a rifle said he was a rather poor shot.

The Single - Bullet Theory

The single-bullet theory is impossible because of the lone-gunman theory note that no bullet in any of the assassination - related wound ballistics tests has emerged with as little damage as the CE 399 the alleged "magic bullet," after doing the same amount of damage that CE 399 supposedly did. They also point to studies that have found that there was no path from Kennedy's back wound to his throat wound that did not require smashing through the spine.

* At least one shot was fired from in front of Kennedy's limousine, most likely from the grassy knoll. Conspiracy theorists point out that dozens of witnesses in Dealey Plaza believed gunfire came from the grassy knoll, and that several witnesses saw puffs of smoke rising from the spot from which the gunfire seemed to be coming. They also note that some rifles do emit visible smoke, and that the HSCA firearms panel confirmed this in its report. They further note that several witnesses smelled the scent of gunpowder on or near the knoll right after the shooting.

* There was a large wound in the right-rear area of Kennedy's skull, indicating a shot from the front. Dozens of witnesses reported seeing this wound, including doctors, nurses, and federal agents. They argue that the autopsy photos of JFK's head, which don't show a large right-rear defect, were either taken after the large defect was covered over cosmetically or that the photos were altered to make it appear the back of the head was undamaged.

* The Zapruder film seems to show reactions to more than just three shots.

* Much of the evidence against Oswald was planted. Oswald was being impersonated, and his impersonators left a trail of false evidence that was to be used against Oswald later.

* There was a rather large-scale cover-up of the facts about the assassination, in an attempt to lead the public to believe there was only one gunman and no conspiracy.

Multiple Shooter Theory

Another theory is that two bullets hit Kennedy and the first of them continued on to hit Connally. The shots were at Zapruder film frames 223 and 312 and the range between Oswald and Kennedy for the first shot was 165 feet, for the second 265 feet. Zapruder's camera speed was 18.3 frames per second, thus the shots were about 5 seconds apart. The bullet which caused President Kennedy's neck wound and Governor Connally's back wound came from a point 27(deg) to the right of true north from the President and was descending at an angle of 25(deg) below horizontal. A straight line can be drawn from Oswald's sniper nest through Kennedy and Connally. Three spent cartridges were found on the sixth floor of the Book Depository, the first shot at frame Z160 having missed. The fact that two bullets made all the wounds makes a multiple-shooter theory unnecessary and ridiculous - why were the phantom shooters such terrible shots that they missed everything?