In the shady world of conspiracy theories, few are murkier or more intriguing than the assassination of President Kennedy in Dealey Plaza on November 22, 1963. Now, nearly 40 years after one of the most notorious crimes of the 20th century, new evidence suggests that a second gunman - not Lee Harvey Oswald - fired the fatal shot.
An intriguing paper in Science and Justice, the respected journal of the Forensic Science Society, turns the evidence back in favour of a conspiracy, saying that the probability of a second gunman on the famous grassy knoll is as high as 96.3 per cent. In statistical terms, that's a certainty.
Don Thomas, a statistician with the US Department of Agriculture, has re-examined the crucial 18 seconds that began when Jesse Curry, the Dallas police chief in the lead car of Kennedy's motorcade, announced on channel two of the police radio that he was approaching the triple underpass at the end of Dealey Plaza. It ended with the chief stating urgently: "Go to the hospital."
What seemed to be a succession of gunshots was picked up on channel one during that interval. The official commission, headed by Earl Warren, then chief justice of the Supreme Court, ignored the recordings. Two subsequent investigations examined them, but could not agree on the number or timing of the mysterious gunshot-like sounds.
Using Curry's words to synchronise events on the police channels was misleading, Dr Thomas has discovered. It led the most recent official examination of the sound recordings, conducted in 1981 by a special panel of the National Academy of Sciences, headed by Harvard professor of physics Norman Ramsey, to conclude that the noises "were recorded about one minute after the president was shot" and emanated from the police motorcycles.
Dr Thomas re-examined the tapes and determined that the analysis by the NAS was flawed and that the gunshot-like noises occurred "at the exact instant that John F Kennedy was murdered". He calculated that the chance of the NAS panel being correct is smaller than 100,000 to one and that the fatal shot almost certainly came from an unknown gunman on the grassy knoll, not Lee Harvey Oswald on the sixth floor of the book depository.
The transmissions were on two channels. One, for routine calls, was preserved on a sound-activated Dictaphone belt, a machine that used a needle to scratch the sound on to grooves in a moving plastic band. A second frequency, dedicated to the motorcade, was recorded on a sound-activated disc machine called a Grey Audograph.
Since 1964, when the Warren commission decided that only three shots were fired by a single assassin - Oswald - from the book depository at the north-east corner of Dealey Plaza, the questions surrounding the tantalising blasts on the police recordings have chipped away at the credibility of their findings. In 1978, the House of Representatives Select Committee on Assassinations re-examined the forensic evidence.
The suspected gunfire blasts were recorded when a motorcycle patrolman inadvertently left his microphone switch in the "on" position, deluging his transmitting channel with what seemed to be motorcycle noise. Using signal analysis techniques, a team from the Computer Sciences Department of City University, New York, filtered out the noise and came up with five "audible events" within a 10-second time frame that it believed might be gunfire.
The House Committee on Assassinations then hired a specialist agency to fire test shots in Dealey Plaza, positioning 36 microphones along the motorcade's route to examine the possibility of a shot coming from the grassy knoll to the side of the limousine. They found 10 echo patterns that matched a gunshot sound emanating from the knoll, travelling carefully measured distances to nearby buildings and then bouncing off them to hit the open motorcycle transmitter.
By comparing the test patterns and oscillograph traces of the cleaned-up police recordings, they deduced that an unknown gunman had fired at least one shot from behind a picket fence at the top of the knoll, in front of and to the right of the limousine, but concluded that this shot missed, and that Kennedy was killed by the final of three bullets from Oswald's rifle.
At last, the question of how many gunmen were involved in the assassination appeared to be solved. But three years later, in 1981, the Justice Department commissioned Prof Ramsey's NAS panel to review the House Committee's findings.
Using the voice heard on both channels of Dallas County Sheriff Bill Decker saying, "Hold everything secure" to synchronise the recordings, it found the gunshot-like noises came a minute after the assassination and concluded there was only a 78 per cent probability that at least one of the bangs was a gunshot from the knoll.
Dr Thomas is now convinced that the National Research Council made crucial mistakes in synchronising the two police recordings because it did not realise that one of the recorders was running five per cent faster than the other and because the needle on the band recorder jumped immediately before Decker's words were recorded on channel one.
To synchronise the two channels, Dr Thomas used a snatch of speech three minutes after the assassination, when Sgt Bellah of the Dallas police asked: "You want me to hold this traffic on Stemmons until we find out something, or let it go?"
Dr Thomas determined that this made a crucial difference. "On channel one, the Decker broadcast is 171 seconds earlier than Bellah's broadcast," he said. "But the Dictaphone was recording five per cent too slow. Adjusting playback to real time, the time lapse is 179 seconds. The Decker broadcast was one second after the last acoustically identified gunshot on that channel. Thus, the suspect noises were simultaneous with the time of the shooting."
Dr Thomas re-worked the statistical analysis of the echo delay time coincidence and found that the grassy knoll marksman was not quite where the 1978 committee placed him, behind a picket fence at the top of the knoll, but a few feet further back, where the fence trails away from the knoll and is hidden by a clump of trees.
"It seems likely the fatal shot came from the grassy knoll because of the mesh between the acoustic evidence and the video evidence, and the medical and ballistic evidence," Dr Thomas added. The video evidence comes from a cine film shot by John Zapruder that formed a key part of previous investigations.
"The Zapruder film shows the president's head driven backwards. Modern studies of enhanced versions of the film show that the fatal shot to the president was at frames 312/313."
The camera used by Zapruder ran at 18.3 frames a second, giving a time interval of 4.8 seconds between the shot that hit Governor Connally and the shot that killed Kennedy.
"The time interval between shots number three and four on the audio tape is also 4.8 seconds, shot four being the acoustically identified grassy knoll shot," Dr Thomas said.
Dr Thomas's finding concur with those of Jean Hill, an eyewitness known as "the Lady in Red" in footage of the assassination. She had always maintained she heard a shot from the knoll, not the book depository, and claimed she ran towards the knoll to see the shooter but was stopped by two policemen.
Prof Ramsey maintains that he is "still fairly confident" in the work of the NAS panel, although he said he did not remember the cross talk of Sgt Bellah's question recorded on both channels. But for Robert Blakey, former chief counsel to the House Assassinations Committee, Dr Thomas's study is a vindication of the committee's work in 1968.
"It shows that we made mistakes, too, but minor mistakes. We thought there was a 95 per cent chance it was a shot. He puts it at 96.3 per cent. Either way, that's beyond a reasonable doubt."
Kennedy Assassination:
New Report Says 2nd Gunman Certainty[Original headline: Who did shoot President Kennedy? ]
Forty years after JFK was assassinated, new evidence reveals that the fatal bullet did not come from Lee Harvey Oswald. Robert Uhlig reports on how crucial mistakes were made because the police tapes of the event were not synchronised
The Telegraph, London / England - April 23 2001
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