DALLAS — Forty years after John F. Kennedy's assassination, an overwhelming majority of Americans do not believe the official conclusion that a loser named Lee Harvey Oswald, acting alone, killed the president with a cheap mail-order rifle fired from the Texas School Book Depository.
Thousands of books, movies and Internet chatrooms have fueled dozens of conspiracy theories that it was a plot by the Mafia, the Cubans, the KGB, the CIA, even Vice President Lyndon B. Johnson, and that other shots came from the grassy knoll or other spots around Dealey Plaza.
Despite four decades of technical improvements in forensics and film enhancement, the questions at the heart of the theories have changed little since Nov. 22, 1963: Who killed Kennedy as he rode in an open Lincoln convertible through downtown Dallas? How many shots were fired? Did Oswald have help?
Oswald, arrested shortly after the assassination, was silenced two days later when nightclub owner Jack Ruby gunned him down as police transferred him from a jail. Answering the question of who was behind the shooting was left to the government-appointed Warren Commission, which after a 10-month investigation concluded in 1964 that Oswald acted alone, firing from the book depository's sixth floor.
Yet, today only 32 percent of American adults accept that finding, according to an ABC News poll. The poll, conducted earlier this month, found that 70 percent think the assassination was part of a broader plot; 51 percent believe there was a second gunman; and more than two-thirds believe there was a government cover-up.
In 1966, three years after Kennedy's death, 46 percent of people surveyed in a Harris poll believed the assassination was part of a broader plot. By 1983, that number had reached 80 percent in an ABC poll.
Some experts have suggested that the Vietnam War and Watergate deepened Americans' cynicism and eroded trust in government.
"Many people look at the Kennedy assassination as a turning point, when people started realizing and thinking and believing their government would lie to them and lie to them repeatedly," said Gary Mack, curator of the Sixth Floor Museum at Dealey Plaza in Dallas.
Perhaps the most persistently questioned finding of the Warren Commission is the "magic bullet" theory.
The theory assumes that Oswald alone fired three shots and that one bullet zigzagged through both Kennedy and Texas Gov. John Connally. The bullet is said to have gone through Kennedy's throat, then into Connally, puncturing his lung, hitting his rib and wrist and then exiting relatively unscathed.
Some historians, forensic experts and conspiracy theorists do not buy it.
James Fetzer, author of "Assassination Science: Experts Speak Out on the Death of JFK," says the Kennedy X-rays and the film of the assassination by bystander Abraham Zapruder were fabricated and that there were actually six or so people firing at the president that day.
"The driver actually brought the limo to a halt to make sure Kennedy was hit enough times to be killed. The Secret Service set him up, and we have more than 15 indications of them doing that," Fetzer said. "The order of vehicles in the motorcade were wrong, that's perhaps the most telling. Nixon knew about it, too. J. Edgar Hoover and LBJ were involved as well, I'm sorry to say."
In 1967, New Orleans District Attorney Jim Garrison asserted that the assassination was a CIA-led coup. Garrison's theories went to court — and eventually to Hollywood as Oliver Stone's 1991 movie "JFK" — but Clay Shaw, the alleged "evil genius" behind the assassination, was acquitted in less than an hour.
Technology has only solidified positions.
Conspiracy theorists now use the Internet to bounce their ideas around the globe, build databases and convert a new generation of believers.
ABC and Court TV both ran sophisticated computer simulations this month of the crime scene and an analysis of a police audiotape, asserting that the Warren Commission got it right — Oswald alone killed Kennedy.
The now-digitized Zapruder film shows exact moments — such as the second when Connally's lapel flew up — that indicate precisely when he was shot and his position relative to the president. Their conclusion: Connally, who sat in front of Kennedy, was turning when he was shot, making the bullet's path plausible.
Many Americans nevertheless find it difficult to believe that a nobody like Oswald — a former Marine who went to live in Russia, became disenchanted with life under communism, and took a dead-end job in Texas — could have single-handedly killed the leader of the free world.
Some 6 million documents have been released by the Assassination Records Review Board, but Kermit Hall, president of Utah State University and one of five people on the board, said he doubts any revelations will come from them.
"The lesson of American history is, by and large, unhappy small-time people, if you will, make more of their life by shooting or killing-better known people," Hall said.