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According to the single-bullet theory, a three-centimeter (1.2″)-long copper-jacketed lead-core 6.5-millimeter rifle bullet fired from the sixth floor of the Texas School Book Depository passed through President Kennedy’s neck and Governor Connally’s chest and wrist and embedded itself in the Governor’s thigh. If so, this bullet traversed 15 layers of clothing, 7 layers of skin, and approximately 15 inches of tissue, struck a necktie knot, removed 4 inches of rib, and shattered a radius bone. The bullet was found on a gurney in the corridor at the Parkland Memorial Hospital, in Dallas, after the assassination. The Warren Commission found that this gurney was the one that had borne Governor Connally. This bullet became a key Commission exhibit, identified as CE 399. Its copper jacket was completely intact. While the bullet's nose appeared normal, the tail was compressed laterally on one side.
In its conclusion, the Warren Commission found "persuasive evidence from the experts" that a single bullet caused the President's neck wound and all the wounds in Governor Connally. It acknowledged that there was a "difference of opinion" among members of the Commission "as to this probability", but stated that the theory was not essential to its conclusions and that all members had no doubt that all shots were fired from the sixth floor window of the Depository building.
Most pro- and anti-conspiracy theorists believe that the single-bullet theory is essential to the Warren Commission's conclusion that Oswald acted alone. The reason for this is timing: if, as the Warren Commission found, President Kennedy was wounded some time between frame 210 and 225 of the Zapruder film  and Governor Connally was wounded in the back/chest no later than frame 240, there would not have been enough time between the wounding of the two men for Oswald to have fired two shots from his bolt action rifle. FBI marksmen, who test-fired the rifle for the Warren Commission, concluded that the "minimum time for getting off two successive well-aimed shots on the rifle is approximately 2 and a quarter seconds" or 41 to 42 Zapruder frames.
In 1979, the House of Representatives Select Committee on Assassinations stated that it agreed with the single-bullet theory but differed on the time frame. The single-bullet theory has been staunchly defended by those who believe the Warren Commission's finding was correct; it has been roundly criticized by those who disagree.
The first preliminary report on the assassination, issued by the FBI on December 9, 1963, said: “Three shots rang out. Two bullets struck President Kennedy, and one wounded Governor Connally.”  After the report was written, the FBI received the official autopsy report which indicated that the bullet that struck the president in the back had exited through his throat. The FBI had written their report partly based on an initial autopsy report written by their agents  which reflected the early presumption that that bullet had only penetrated several inches into the president's back and had likely fallen out. The FBI concluded, therefore, that the governor had been struck by a separate bullet.
The Warren Commission commenced study of the Zapruder film, the only known film to capture the entire assassination sequence, on January 27, 1964. By then, the FBI had determined that the running speed of Abraham Zapruder's camera was 18.3 frames per second, and that the Mannlicher-Carcano rifle found at the Texas School Book Depository, the presumed murder weapon, could not be fired twice in less than 2.3 seconds, or 42 frames of the Zapruder film.
When the Commission requested and received after February 25 higher-resolution images of the Zapruder film from Life magazine (who had purchased the film from Zapruder), it was immediately apparent that there was a timing problem with the FBI's conclusion that three bullets had found their mark. Kennedy was observed by the Commission to be waving to the crowd to frame 205 of the Zapruder film as he disappears behind the Stemmons Freeway sign, and seems to be reacting to a shot as he emerges from behind the sign at frames 225-226, a little more than a second later. In their initial viewing of the film, Connally seemed to be reacting to being struck between frames 235 and 240.
Given the earliest possible frame at which Kennedy could have been struck (frame 205), and the minimum 42 frames (2.3 seconds) required between shots, there seemed to be insufficient time for separate bullets to be fired from the rifle. Several assistant counsels, upon viewing the film for the first time, concluded there had to be two assassins.
On April 14 and 21, two conferences were held at the Commission to determine when, exactly, the president and governor were struck. Assistant counsel Melvin Eisenberg wrote in a memorandum dated April 22 on the first conference that the consensus of those attending was, among other issues, that Kennedy was struck by frames 225–6 and that “the velocity of the first bullet [which struck Kennedy] would have been little diminished by its passage through the President. Therefore, if Governor Connally was in the path of the bullet it would have struck him and caused the wounds he sustained in his chest cavity... Strong indications for that this occurred are provided by the facts that... if the first bullet did not strike Governor Connally, it should have ripped up the car but it apparently did not.” However, the memorandum stated, given the relatively undamaged condition of the bullet presumed to have done this, CE 399, the consensus was a separate bullet probably struck his wrist and thigh. While not specifying a precise frame for when it was thought Connally was struck by the same bullet which struck Kennedy, the consensus was “by Z235” as afterwards his body position would not have allowed his back to be struck the way it was.
By the end of April 1964, the Commission had its working theory, the single-bullet theory, to account for the apparent timing discrepancies found in the Zapruder film and the lack of any damage to the limousine from a high-velocity bullet exiting the president's throat. (Impact damage was observed in the limousine, but was indicative of lower-velocity bullets or bullet fragments. For example, a nick on the limousine’s chrome was not from a high-velocity bullet as such a bullet would have pierced the chrome, not merely dented it.)
On May 24, the FBI and Secret Service reenacted the shooting in Dallas and the Commission tested its theory. Agents acting as the president and the governor sat in a car of approximately the same dimensions of the presidential limousine, which was unavailable for the recreation. Adjustments to measurements were made to account for the differences in the vehicles. Positions were recreated by matching them to particular frames of the Zapruder film, calibrated with other films and photographs taken that day. With the agents in position, photographs were taken from the sniper’s nest of the Texas School Book Depository. It was from this recreation, and the testimony of the agent in the sniper’s nest, that the Commission verified the theory to its satisfaction, as the governor was in a direct line to be struck by any bullet fired between frames 207 and 235 to 240 which exited the president’s throat, though the agent in fact testified that from frame 226 onward the governor was “too much towards the front” and his wounds were therefore misaligned from that point. An oak tree partially obscured the line of sight until frame 210, so the Commission concluded that “the President was not hit until at least frame 210 and that he was probably hit by frame 225.”
Further evidence gathered suggested to the Commission that the initial April consensus that a separate bullet caused the governor’s wrist and thigh injuries was incorrect, as the Army Wound Ballistics experts concluded that those wounds were “not caused by a pristine bullet,” and therefore bullet CE 399 “could have caused all his wounds.” Other evidence, such as the nature of Connally’s back wound (see below) was also cited by the Commission as corroborating the theory.
The Commission, however, did not conclude the single-bullet theory had been proven, as three members of the body, Representative Hale Boggs, Senators Richard Russell and John Cooper thought the theory improbable. Russell requested that his opposition to the theory be stated in a footnote in the report. In the end, the Commission changed the word “compelling” to “persuasive” and stated: “Although it is not necessary to any essential findings of the Commission to determine just which shot hit Governor Connally, there is very persuasive evidence to indicate that the same bullet which pierced the President’s throat also caused Governor Connally’s wounds.”
Nevertheless, all seven members of the Commission signed off on the statement: “There was no question in the mind of any member of the Commission that all the shots which caused the President’s and Governor Connally’s wounds were fired from the sixth floor window of the Texas School Book Depository.”
Within minutes after the shots rang out in Dealey Plaza in downtown Dallas, Texas, at 12:30 p.m. on November 22, 1963, independent sources began reporting that three shots had been fired at the President’s motorcade. At 12:34 p.m., approximately four minutes after the shots were fired, the first wire story flashed around the world:
“DALLAS NOV. 22 (UPI) -- THREE SHOTS WERE FIRED AT PRESIDENT KENNEDY’S MOTORCADE TODAY IN DOWNTOWN DALLAS. JT1234PCS”
This report had been transmitted by United Press International reporter Merriman Smith from a radio telephone located in the front seat of the press car in the Presidential motorcade, six cars behind the President’s limousine. Smith’s communication with the Dallas UPI office was made less than a minute after the shots were heard, as his car entered the Stemmons freeway en route to Dallas’ Parkland Hospital.
Merriman Smith’s dispatch was the first of many reports. There were dozens of journalists riding in the motorcade in three open press cars and a press bus, none of whom reported hearing a number of shots other than three. Photographers Robert Jackson and Tom Dillard riding in a car in the motorcade heard three shots. The Dallas Morning News reporter Mary Woodward described hearing three shots as she stood in front of the Texas School Book Depository.
There has been some controversy over the number of shots fired during the assassination. The Warren Commission concluded that three shots were fired. The vast majority of witnesses claim to have heard three, but there are some witnesses who could recall only one or two shots. A few witnesses thought there were four or more shots. Of 178 witnesses whose evidence was compiled by the House Select Committee on Assassinations (HSCA), 132 reported hearing exactly three shots, 17 recalled hearing two, 7 said they heard two or three shots (total: 88%). A total of 6 people said they thought they heard four shots, and 9 said they were not sure how many shots they heard. Another 7 people said they thought they heard 1, 5, 6, or 8 shots.
Governor Connally, riding in the middle jump seat of the President's limousine in front of the President, recalled hearing the first shot which he immediately recognized as a rifle shot. He said he immediately feared an assassination attempt and turned to his right to look back to see the President. He looked over his right shoulder but did not catch the President out of the corner of his eye so he said he began to turn back to look to his left when he felt a forceful impact to his back. He stated to the Warren Commission: "I immediately, when I was hit, I said, “Oh, no, no, no.” And then I said, “My God, they are going to kill us all.” He looked down and saw that his chest was covered with blood and thought he had been fatally shot. Then he heard the third and final shot, which sprayed blood and brain tissue over them.
Nellie Connally said she heard the first shot and saw President Kennedy with his hands at his neck reacting to what she later realized was his neck wound. After the first shot, she heard her husband yell, "Oh, no, no, no" and turn to his right (away from her). Then she heard a second shot, which hit her husband. She saw him recoil away from her and saw that he was hit. She immediately reached over and pulled him toward her into her arms and lay backward. Then she heard the third and final shot. Mrs. Connally said she never looked into the back seat of the car after her husband was shot.
According to the single-bullet theory, one shot passed through President Kennedy's neck and caused all of Governor Connally's wounds (he was wounded in the chest, right wrist, and left thigh), and one of the shots must have missed the limousine entirely. The Connallys never accepted the theory. While they agreed with the Warren Commission's conclusion that Oswald acted alone, they insisted that all three shots struck occupants of the limousine.
President Kennedy's death certificate places the bullet wound to Kennedy's back at the third thoracic vertebra. The death certificate was signed by Dr. George Burkley, the President's personal physician. As interpreted by the House Select Committee on Assassinations Forensic Pathology Panel, the autopsy photos and autopsy X-rays show a bullet hole at the first thoracic vertebra. The bullet hole in the shirt worn by Kennedy and the bullet hole in the suit jacket worn by Kennedy both show bullet holes between 5 and 6 inches (13 and 15 cm) below the top of Kennedy's collar. These do not necessarily correspond with bullet wounds, since Kennedy was struck with his arm raised, and multiple photos taken of the President during the motorcade show that his jacket was bunched in the rear below his collar. In addition, on February 19, 2007, the film shot by George Jefferies was released. This 8 mm film, taken approximately 90 seconds before the shooting, also clearly shows that President Kennedy's suit coat was bunched up around the neckline around the time of the assassination.
The theory of a "single bullet" places a bullet wound as shown in the autopsy photos and X-rays, at the first thoracic vertebra of the vertebral column. The official autopsy report on the President, Warren Exhibit CE 386  described the back wound as being oval, 6 x 4 mm, and located "above the upper border of the scapula" [shoulder blade] at a location 14 cm (5.5 in) from the tip of the right acromion process, and 14 cm (5.5 in) below the right mastoid process (the boney prominence behind the ear). The report also reported contusion (bruise) of the apex (top tip) of the right lung in the region where it rises above the clavicle, and noted that although the apex of the right lung and the parietal pleural membrane over it had been bruised, they were not penetrated. The report also noted that the thoracic cavity was not penetrated.
The concluding page of the Bethesda autopsy report states: "The other missile [referring to the body-penetrating bullet] entered the right superior posterior thorax above the scapula, and traversed the soft tissues of the supra-scapular and the supra-clavicular portions of the base of the right side of the neck. This missile produced contusions of the right apical parietal pleura and of the apical portion of the right upper lobe of the lung. The missile contused the strap muscles of the right side of the neck, damaged the trachea, and made its exit through the anterior surface of the neck."
Many years after the Warren Commission report, Representative Gerald Ford stated that he had changed a draft of the Warren Report to indicate that the bullet entered the "base of the back of [Kennedy's] neck" rather than "his back at a point slightly above the shoulder", but said he did not do it as part of a conspiracy. The original Bethesda autopsy report, included in the Warren Commission report, concluded from the data this bullet had passed above the top of the lung outside the thoracic pleura and, therefore, through the president's neck. Ford's description also matched a drawing prepared for the Commission under the direction of Dr. James J. Humes, supervisor of Kennedy's autopsy. In his testimony to the Commission, Humes said three times that the entrance wound was in the "low neck." The Commission was not shown the autopsy photographs.
The conclusion of bullet entry specifically at the first thoracic vertebra was made in a 1979 report on the Kennedy assassination by the HSCA Forensic Pathology Panel, which created Figure  for their report to demonstrate this entrance location. This position is consistent with the back wound location in Figure 4 of their report, a drawing made from one of the still-unreleased autopsy photos. It is also consistent with the unofficial versions of this photo available on the internet. The HSCA examined these photographs and X-rays before rendering its opinions as to bullet entry and exit locations, and obtained testimony from autopsy physicians that these were the correct photographs and X-rays taken during the autopsy.
The importance of how low or high the bullet struck the President in the back is a matter of possible geometry. The Sibert/O'Neill FBI autopsy report original made by two FBI agents (Special Agents James W. Sibert and Francis X. O'Neill) present at the autopsy preserves genuine confusion amongst medical doctors present during the autopsy, caused by apparent lack of an exit wound, which was cleared up later in the official report after new and more complete information became available (the exit had been hidden by a tracheotomy incision). This report does note that the doctor (Commander Humes) at the time said that he was unable to locate an "outlet" for the wound in Kennedy's shoulder (not his back).
At the time of the autopsy, toward the end of the procedure, initial probing of the shoulder wound suggested the bullet entered the base of Kennedy's neck at a 45 to 60 degree angle. The bullet was believed to have been fired from the sixth floor window in the north-east corner of the Texas Book Depository. The Warren Commission had the angles from that window to the location of the President at frames 210 and 225 of the Zapruder film measured by surveyors. It was found that the downward angle from the horizontal was 21.57 degrees at frame 210, and 20.18 degrees at frame 225. The street sloped at 3.15 degrees (3° 9') away from the Depository,. This would have made the angle through the President between 17 and 18.5 degrees, assuming the President was sitting upright in his seat. The Commission concluded that this angle was consistent with the bullet making the observed paths through the President's upper body and striking Governor Connally in the right armpit.
The weight of bullet CE399 was reported in the Warren Commission Report as 158.6 grains (10.28 grams). It was found that the weight of a single, unfired bullet ranged from 159.8 to 161.5 grains with an average weight of 160.844 grains. The lead fragments retrieved from Connally's wounds in the wrist (there were no fragments in the chest) weighed about 2 grains (130 milligrams).
Dr. Robert Shaw described the wound on Connally's back as "a small wound of entrance, roughly elliptical in shape, and approximately a cm. and a half in its longest diameter, in the right posterior shoulder, which is medial to the fold of the axilla".
The bullet entered just at the edge of the scapula and followed the fifth rib, shattering the last 10 cm of the rib before exiting on the right side of his chest just below the right nipple. According to the theory, the bullet then went through the Governor's jacket cuff about .5 cm from the end, the shirt's French cuff about 1.5 cm from the end, struck and shattered his radius leaving many dark fibres and small fragments of metal in the wound, and exited on the palm side of his wrist above the cuff. There was a hole about .5 cm from the end of the jacket sleeve and a hole through the back of the doubled French cuff but no exit hole on the palm side.
According to the theory, the bullet emerged from the palm side of the wrist and entered the left thigh. This bullet is thought to be CE 399 which was recovered from Governor Connally's stretcher later at Parkland Hospital. CE 399 was ballistically matched to the rifle found in the Texas Schoolbook Depository, to the exclusion of all other rifles.
The following description assumes that bullet CE 399 hit high, at the sixth cervical vertebra rather than the third thoracic vertebra: The 6.5 millimeter, 161 grain, round nose military style full metal jacket bullet, which was manufactured by the Western Cartridge Company and later stored nearly whole in the U.S. National Archives, was first theorized by the Warren Commission to have:
Regarding the bullet that he remembered impacting his back, Connally stated, "...the most curious discovery of all took place when they rolled me off the stretcher and onto the examining table. A metal object fell to the floor, with a click no louder than a wedding band. The nurse picked it up and slipped it into her pocket. It was the bullet from my body, the one that passed through my back, chest, and wrist, and worked itself loose from my thigh." Connally does not say how he determined this object to have been a bullet, rather than his missing gold cufflink.
The Warren Commission's "single bullet," according to all documentation:
This "single bullet," which was full metal jacketed and specifically designed to pass through the human body, was deformed and not in a pristine state as some detractors claim. Though a side view seems to show no visible damage, a view from the end of the bullet shows a significant flattening which occurred when, according to the theory, the bullet struck Connally's wrist, butt end first. The metallurgical composition of the bullet fragments in the wrist was compared to the composition of the samples taken from the base of CE 399.
Several of the same type 6.5 millimeter test bullets were test-fired by the Warren Commission investigators. The test bullet that most matched the slight side flattening and nearly pristine, still rounded impact tip of CE 399 was a bullet that had only been fired into a long tube containing a thick layer of cotton. Later tests show that such bullets survive intact when fired into solid wood and multiple layers of skin and ballistic gel, as well.
CE 399 is stored out of the public's view in the National Archives and Records Administration, though numerous pictures of the bullet are available on the NARA website.
Ballistics experts have performed test shots through animal flesh and bones with cloth covering. Under the assumption of an adjusted relative position of President Kennedy and Governor Connally within the car, some, but not all, of the Warren Commission ballistics experts considered it possible that the same bullet that passed through the President's neck may have caused all of the governor's wounds. The Warren Commission as a whole wrote that it was persuaded that the President's neck wound and all of the governor's wounds were caused by a single bullet, although three of the seven members, Sen. Richard Russell, Rep. Hale Boggs, and Sen. John Cooper, have stated that they did not support the theory because it did not fit the evidence.
In 2004, the Discovery Channel aired an episode of Unsolved History titled JFK — Beyond the Magic Bullet. Their re-enactment of the assassination using current forensics and materials found that a single bullet almost exactly duplicated the path of travel specified in the single bullet theory.
In 1993 a computer animator named Dale Myers embarked on a 10-year project to completely render the events of November 22 in 3D computer animation. His results were shown as part of ABC's documentary The Kennedy Assassination: Beyond Conspiracy in 2003, and won an Emmy award.
To render his animation, Myers took photographs, home footage, blueprints and plans, and attempted to use them to create an accurate computer reenactment of the assassination. His work was assessed by Z-Axis who have been involved in producing computer generated animations of events, processes and concepts for major litigations in the United States and Europe.
Their assessment concluded that Myers' animation allowed the assassination sequence to be viewed "from any point of view with absolute geometric integrity" and that they "believe that the thoroughness and detail incorporated into his work is well beyond that required to present a fair and accurate depiction."
Myers' animation found that the bullet wounds were consistent with JFK's and Governor Connally's positions at the time of shooting, and that by following the bullet's trajectory backwards it could be found to have originated from a narrow cone including only a few windows of the sixth floor of the School Book Depository, one of which was the sniper's nest of boxes from which the rifle barrel had been seen protruding by witnesses.
In the same ABC documentary, Myers uses a close-up examination of the Zapruder film to justify the single-bullet theory and calls attention to frames 223 and 224 on the Zapruder film where the right side lapel of Governor Connally's jacket appears to "pop out," as if being pushed from within by an unseen force. Myers theorizes that this is the moment of impact, when both Kennedy and Connally were struck by the same bullet from Oswald's rifle. Myers also argues out that in frames 225-230 both Kennedy and Connally are simultaneously reacting to the impact of the bullet.
If the bullet exited Connally's chest below the nipple the lapel would be too high to have popped out due to direct contact with the bullet but surgeon John Lattimer has argued that jacket bulged out because of the "hail of rib fragments and soft tissue" as the bullet tumbled in Connally's body.
Warren Commission documents released after the publication of its report revealed that the FBI had arranged for bullet CE 399 and the various fragments found in the car and in Governor Connally’s wounds to be examined using a method known as neutron activation analysis (NAA). NAA is a very accurate, non-destructive method of determining the relative concentrations of trace elements in a sample of matter. The data from the tests performed for the FBI were inconclusive as to the origins of the fragments.
In 1978 the HSCA asked physicist Vincent P. Guinn to review the NAA data and conduct new tests. Guinn did so and presented his results and analysis to the Committee. Guinn stated that initially he agreed with the earlier conclusion. However, after examining the old and new NAA data further, he concluded that all the fragments probably came from two bullets, one of which was the whole bullet, CE 399.
Guinn compared antimony concentrations of Exhibits CE 840, 843 and 567 with that of Exhibits CE 399 and 842 and concluded that the data supported the single-bullet theory in that all the bullet lead in the car and wounds originated from no more than two bullets.
Whether the NAA data can be used to actually exclude the possibility that there were fragments from more than two bullets in the wounds and the car has been the subject of controversy.
Ken Rahn of the University of Rhode Island, a chemist and meteorologist who has a long standing interest in the Kennedy Assassination, maintains that the NAA data excludes a “three bullet hit” and proves the SBT actually occurred. His analysis was published in 2004  co-authored with Larry Sturdivan, a Warren Commission and HSCA ballistics expert.
Rahn/Sturdivan say that the possibility that the wrist fragment CE 842 (with an antimony concentration of 797 ± 7 ppm) did not come from the base of the whole bullet CE 399 (the sample from which had an antimony concentration of 833 ± 9 ppm) is so statistically improbable as to be excluded as a reasonable possibility.
However, in an article published in July 2006 in the Journal of Forensic Science by Erik Randich and Patrick M Grant, the authors took a much different view of the NAA data and the metallurgical profile of the Mannlicher-Carcano ammunition. The authors found errors in the analysis by Guinn:
Thus, elevated concentrations of antimony and copper at crystallographic grain boundaries, the widely varying sizes of grains in MC bullet lead, and the 5–60 mg bullet samples analyzed for assassination intelligence effectively resulted in operational sampling error for the analyses. This deficiency was not considered in the original data interpretation and resulted in an invalid conclusion in favor of the single-bullet theory of the assassination.
Randich and Grant concluded:
The end-result of these metallurgical considerations is that, from the antimony concentrations measured by VPG [Vincent P. Guinn] in the specimens from the JFK assassination, there is no justification for concluding that two, and only two, bullets were represented by the evidence.
The conclusion of Randich and Grant had been advanced earlier by Arthur Snyder of the Stanford Linear Accelerator Laboratory in a paper written in 2001.
In August 2006 Ken Rahn wrote a response critical of the Randich/Grant paper. claiming that Randich and Grant did not analyse the data correctly:
Both sections of the article failed to make their case. The metallurgical section contained a huge gap in its logic (proposing an explanation but failing to support it quantitatively), and predicted at least two features of the elemental data that were the opposite of that actually observed. The statistical section started well, but stumbled when it confused heterogeneity with analytical uncertainty and when it used confidence intervals instead of difference in means to assess the separation of the two groups of crime-scene fragments. Fixing these two errors gave the opposite result, i.e., confirmed that the groups were distinct.
The technique used by Guinn to analyse the bullet lead from the JFK assassination was a form of what has become known as Compositional Bullet Lead Analysis (CBLA). Until 2004 the FBI used this technique to determine whether a crime scene bullet lead sample came from a particular box of ammunition or a particular batch of bullets. Guinn claimed that with the JFK bullet fragments, the technique could be used to identify the exact bullet the fragments came from.
However, the validity of CBLA was discredited in a 2002 paper ("A Metallurgical Review of the Interpretation of Compositional Bullet Lead Analysis", (2002) 127 Forensic Science International, 174-191) co-authored by Randich and by former FBI Chief Metallurgist, William Tobin.
The 2002 Tobin/Randich paper prompted the National Academy of Sciences (Board on Chemical Science and Technology) to review the science of bullet lead analysis. In a report in 2004 the NAS found the scientific basis for matching bullet sources from the analysis of bullet lead composition as practiced by the FBI was flawed. As a result of that report, the courts appear to have stopped accepting this evidence and the FBI has stopped using bullet lead analysis for forensic purposes.
The NAS report on CBLA, and its relevance to the Guinn's analysis of bullet lead in the JFK assassination, is the subject of comment by Randich and Grant in their 2006 paper at page 719.
Critics claim that a bullet that passed through several layers of clothing and flesh, destroyed a five inch (127 mm) section of a rib, broke a wrist radius bone, and shed metal fragments (some of which are buried with Connally) could not be in such nearly pristine shape, especially given that the, supposedly, same type "headshot" bullet, according to the Warren Commission, completely broke apart after passing through only two layers of less-dense skull bone.
Critics of the single-bullet thesis question not only the bullet's trajectory and relative lack of damage, but also the question of timing of hits to both the president and Connally. A single bullet would have passed through both men in less than 1/100th of a second, which means that a strike of both men by a single bullet would have happened too quickly to be caught on more than a single Zapruder frame (these were exposed at 1/18th second intervals). From the Zapruder film one can see Kennedy with his hands in front of his chest near his throat as he emerges from behind the sign at Zapruder frame 225.
According to one popular version of the single-bullet theory (promoted by Gerald Posner in his book, Case Closed), the interval between frame 223 and 224 is the time the same projectile passes through both JFK and Connally's body. It is not obvious at this point (frame 224), whether Connally has, or has not, been hit; however Connally, but not other limousine occupants, is newly blurred in frame 224 but not in frame 223. Connally himself, in analyzing the frame-by-frame Zapruder film, identified his own hit later, at about Zapruder frame 230, whereas JFK is certainly hit about Zapruder frame 224, a third of a second earlier. Beginning immediately after frame 224, Connally rapidly raises and then lowers both arms, then turns to his right toward the Zapruder camera, but it is not clear that he is turning to see what has happened to Kennedy.
He must have been hit before this point, if hit by the same bullet, since the President is already reacting. Connally's cheeks then puff out, and his mouth opens. Many suggest that he is beginning to show the shock of the bullet. Others suggest that Connally is doing exactly what he said he did in reaction to hearing the first bullet: he said he realized an assassination was unfolding so he turned to see the President. It is at this point that some critics of the single-bullet theory believe Connally is actually hit by a second and separate bullet, and this is also what Connally himself believed, but only on the supposition that the first shot he heard was one that struck the president. (If the first shot missed the president, then Connally's memory of being hit later corresponds with the single-bullet theory.) Proponents of the single-bullet thesis argue that Connally is simply exhibiting a delayed pain reaction to having been hit by the same bullet that hit Kennedy, a third of a second earlier.
Some critics believe the puffing out of Connally's cheeks is simply physics at work, as the bullet collapses one of his lungs, forcing air into his mouth. Other critics believe that the puffing of Connally's cheeks result from him shouting, "Oh, no, no, no", which his wife, Nellie, said he shouted after the first shot but before the second shot. The premise that a collapsed lung would cause Connally's cheeks to puff out is dismissed by Dr. Michael Baden, chief forensic pathologist for the HSCA. "When the lung is punctured, as Connally's was, the air in the lung goes out into the chest cavity, not out of the mouth, so Connally's cheeks puffing out would have not been caused by air trying to escape."
When an enhanced copy of the Zapruder film was released in 1998, many felt the delayed reaction theory was debunked. Others, particularly Posner, noted that Connally's right lapel flips up at frame 224 (it hides the right part of his white collar in frame 224, which is far more clearly seen in both frames 223 and 225). In this same frame, as noted above, Connally suddenly becomes blurred with regard to the rest of the automobile (Connally is clear in frame 223). Frame 224 is precisely the best-posited frame of the impact of the bullet to Kennedy, who is still behind the sign at this point. Zapruder himself does not appear to jump until frame 227, blurring all contents of the automobile.
Connally's immediate reaction after frame 224, including a flinch in which he flexes both elbows and brings his hat up, is seen by some as an unconscious reaction to the strike (single frames of this reaction appear to show Connally unharmed, with hat held up in front of his chest, while Kennedy behind him has already clearly been hit). Others see this as the Governor's reaction to the sound of the first shot. Immediately after the arm spasm, Connally begins a motion which drops his right shoulder and holds his right arm pinned to his right side, including a slow rolling motion toward this side. He also is seen to look over his right shoulder at Kennedy and shows an expression of pain only after turning his head back toward Zapruder's position around frame 275. Some believe[who?] that Connally was hit in the chest just before frame 275.
In the Oliver Stone movie JFK, Stone goes to great lengths to debunk the single-bullet theory, although some discrepancies exist between the narrative and the historical record. One example is when he shows both Kennedy and Connally seated directly in front of each other at the same height. In fact, Connally was seated in a jump seat the edge of which was 3 inches inboard and possibly 4 inches lower than Kennedy.
The House Select Committee concluded that the Governor could have been as much as 6 inches (15 cm) to the left of the President. Moreover, Stone has Connally looking straight ahead. However, when Connally emerges from behind the freeway sign at Zapruder frames 222-223, he is clearly rotated significantly to his right. These points are of critical importance in assessing whether the bullet that passed through Kennedy could have caused Connally's injuries. Computer recreations showing accurate body positioning of the two men show that their injuries, if caused at Zapruder frame 224, fall on a line which emanates from a circle enclosing several windows on the sixth floor of the Texas Book Depository, and includes the window of the sniper's nest.
Connally continued to hold his hat after the single bullet struck and broke his right wrist. Critics contend this is not physically possible. However, in the Zapruder film Connally continues to clutch the hat even after Kennedy's head wound, this being a point after which everyone (including critics) agree Connally must have already been hit. In fact, Connally's wife, Nellie Connally, stated that he held on to his hat until he was put on a stretcher at Parkland Hospital. Thus, it is reasonably clear that Connally continued to hold the hat after being hit. Wrist fracture would not preclude ability to hold a light object such as a hat, and Connally's nerve damage was limited to a superficial branch of the radial nerve which served a sensory function only, and would not have interfered with his grip strength (nor was Connally's hand function in any way permanently harmed).
Another criticism that has been made of the single-bullet theory is that it requires a missed shot. The Warren Commission Report contained a subchapter entitled "The Shot that Missed". The Warren Commission concluded, based on the "preponderance of evidence," that one shot probably missed the Presidential limousine and its occupants. "The Shot that Missed" addresses each of the three shots and provides the arguments for and against such a shot missing. However, the Commission stated that "the evidence is inconclusive as to whether it was the first, second, or third shot which missed." The HSCA, in contrast, concluded that the shot that missed was the first shot, and that shot was fired at approximately frame 160 of the Zapruder film.
A further criticism of the single-bullet theory has to do with the apparent trajectory of the "single bullet". Perhaps the most outspoken critic of the single-bullet theory has been pathologist Dr. Cyril Wecht who, as a member of the House Select Committee on Assassinations, wrote a dissenting opinion in which he explained why, in his view, the left to right trajectory from the sixth floor window of the Texas School Book Depository through the President's neck could not possibly intersect with Governor Connally's right armpit. Wecht notes that in the photographs it appears that Governor Connally is seated in the middle of the jump seat and the President is to the right side of his seat with his right arm resting on the top of the limousine side.
According to the analysis done by the HSCA, the horizontal angle from the 6th floor window of the Texas School Book Depository to the limousine at frame 190 or so was about 13 degrees, right to left. The vertical angle was about 21 degrees downward from the horizontal plane and 18 degrees relative the car which was going down at 3 degree slope.
If Governor Connally was seated in the middle of his seat, the bullet should have struck the Governor to the left of his spine. The HSCA concluded that the thigh wound was made by a bullet travelling at a much slower speed than one would expect the bullet to have after exiting the President's neck (though the single-bullet theory holds that the bullet which struck Connally's thigh had also passed through his wrist, slowing it down in the process). Governor Connally said that he never felt this thigh wound at any time until the next day. On the other hand, Dr. Shires, who operated on Governor Connally's thigh wound, thought that the wound to the thigh (which he said extended to the region of the femur) could have been made by a bullet travelling at high speed striking the thigh on an angle.
The HSCA concluded, however, that Governor Connally was not seated in the middle of his seat but was about 7-8 inches to the left of that position. NASA Engineer Thomas Canning provided an analysis of the photograph taken by Hugh Betzner from the rear of the limousine a moment prior to the first shot (according to Betzner, he took the picture and began winding his camera to take another when the first shot sounded). It has been determined that Betzner's photograph was simultaneous with Zapruder frame 186. Mr. Canning could not see the Governor's shoulder in Betzner's photograph and concluded that this meant that the shoulder was obscured by the person standing in front of Betzner. This, he said, put the shoulder well to the left of the president's midline putting his right armpit in line with a right-to-left path through the President's neck. The analysis and conclusion of Canning depends on the correctness of the assumption that Governor Connally's shoulder would have been visible if the man in front of Betzner was not there. The photo taken by James Altgens taken from a similar angle earlier on Houston Street would seem to indicate that Governor Connally's shoulder was below the line of sight.
The single-bullet theory as proposed by the House Select Committee on Assassinations and later by author Gerald Posner in his book Case Closed (which is that the first shot missed and the second shot passed through both the President and the Governor) has also been criticised on the grounds that it does not fit the shot pattern recalled by most of the witnesses (which was: first shot, a longish pause and then two shots in rapid succession, the second shot being after the midpoint between the first and last shots). The Warren Commission remarked on the "substantial majority" of witnesses who recalled that the shots were not evenly spaced but did not attribute much significance to the shot pattern. If the first shot occurred after frame 150 of the Zapruder film, the second shot could not have occurred before frame 240 in order to have a shot pattern in which the last two shots were noticeably closer together (the head shot obviously occurred between frames 312 and 313).
If the last two shots were closer together, Governor Connally was either wounded in the back on the first shot or he was not wounded until many frames after frame 240. This "late hit" view was abandoned in April 1964 because the FBI expert Robert Frazier expressed the opinion (as did Governor and Mrs. Connally) that the Governor must have been hit in the chest by frame 240.
The Governor said that he reacted to the sound of the first shot (which he immediately recognized as a rifle shot) by turning to his right and trying to see the President:
"I heard this noise which I immediately took to be a rifle shot. I instinctively turned to my right because the sound appeared to come from over my right shoulder, so I turned to look back over my right shoulder, and I saw nothing unusual except, just people in the crowd, but I did not catch the President in the corner of my eye, and I was interested, because once I heard the shot in my own mind I identified it as a rifle shot, and I immediately-the only thought that crossed my mind was that this is an assassination attempt." 
Some critics have questioned the circumstances surrounding the bullet's discovery at Parkland Hospital. In a 1966 interview with author Josiah Thompson, one of the men who found the bullet, Parkland personnel director O.P. Wright, cast doubt on whether the bullet subsequently entered into evidence as CE 399 was the same bullet he held in his hand that day. Wright told Thompson that the bullet they found was point nosed, whereas CE 399 is round nosed. However, in 1964, both Wright and Darrel Tomlinson, a maintenance employee at Parkland who passed the bullet along to Wright, were shown the bullet and said the bullet in evidence appeared to be the same one as the bullet found on the stretcher, though neither could positively identify the bullet as the same one.
I have been accused of changing some wording on the Warren Commission Report to favor the lone-assassin conclusion. That is absurd. Here is what the draft said: "A bullet had entered his back at a point slightly above the shoulder and to the right of the spine.” To any reasonable person, “above the shoulder and to the right” sounds very high and way off the side — and that’s what it sounded like to me. That would have given the totally wrong impression. Technically, from a medical perspective, the bullet entered just to the right at the base of the neck, so my recommendation to the other members was to change it to say, “A bullet had entered the back of his neck, slightly to the right of the spine.” After further investigation, we then unanimously agreed that it should read, “A bullet had entered the base of his neck slightly to the right of the spine.” As with any report, there were many clarifications and language changes suggested by several of us.