BOSTON, Oct 26 (Reuters) - More than half a century after U.S. President John F. Kennedy was struck down by an assassin's bullet in Dallas, Texas, the United States is due on Thursday to release the final files on the investigation into the killing that rattled a nation.
Academics who have studied Kennedy's slaying on Nov. 22, 1963, said they expected the final batch of files to offer no major new details on why Lee Harvey Oswald gunned down the first and only Irish-American Roman Catholic to hold the office.
They also feared that the final batch of more than 5 million total pages on the Kennedy assassination held in the National Archives will do little to quell long-held conspiracy theories that the 46-year-old president's killing was organized by the Mafia, by Cuba, or a cabal of rogue agents.
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(GERMANY OUT) Attentat / Kennedy-Attentat: Lee Harvey Oswald steht im Vorgarten eines amerikanischen Wohnhauses und hÃ¤lt ein Gewehr in der Hand. An der Seite trÃ¤gt er eine Pistole mit Halfter. Mit der rechten Hand hÃ¤lt er sich ein SchriftstÃ¼ck, mÃ¶glicherweise eine Zeitung, vor die Brust. Am 22. November 1963 tÃ¶tet Oswald den amerikanischen PrÃ¤sidenten bei einem Besuch im texanischen Bundesstaat Dallas. Nach seiner Verhaftung wird der 24-jÃ¤hrige von dem Nachtclubbesitzer Jack Ruby ermordet. Undatiertes Foto. (Photo by Thomas & Thomas/ullstein bild via Getty Images)
Dallas. Texas. Location of the scene where John Kennedy was assassinated during an official journey, 1963, United States, National archives. Washington, . (Photo by: Photo12/UIG via Getty Images)
American president John F. Kennedy (1917 - 1963) is struck by an assassin's bullet as he travels through Dallas in a motorcade, 22nd November 1963. In the car next to him is his wife Jacqueline (1929 - 1994) and in the front seat is Texas governor John Connally. (Photo by Three Lions/Hulton Archive/Getty Images)
The view from the sixth floor window of the Texas School Book Depository in Dallas, from which Lee Harvey Oswald is thought to have assassinated President John F. Kennedy, 22nd November 1963. This photograph was taken approximately one hour after the assassination. (Photo by Hulton Archive/Getty Images)
NEW YORK - NOVEMBER 22: CBS News anchor Walter Cronkite reports President John F. Kennedy assassinated in Dallas, TX on Friday, November 22, 1963. (CBS via Getty Images)
23rd November 1963: Mugshot of Lee Harvey Oswald (1939 - 1963), alleged assassin of President John F. Kennedy, taken by the Dallas Police department, Dallas, Texas. (Photo by Hulton Archive/Getty Images)
In the aftermath of the assasination of US President John F. Kennedy, American politician and Vice-President Lyndon Baines Johnson (1908 - 1973) takes the oath of office to become the 36th President of the United States as he is sworn in by US Federal Judge Sarah T. Hughes (1896 - 1985) (left) on the presidential aircraft, Air Force One, Dallas, Texas, November 22, 1963. Kennedy's widow, Jacqueline Lee Bouvier Kennedy (later Onassis) stands beside him at right. (Photo by Universal History Archive/Getty Images)
Lee Harvey Oswald (1939 - 1963) (R), alleged assassin of President John F. Kennedy, is detained by a police officer while under arrest, Dallas, Texas, November 1963. (Photo by Hulton Archive/Getty Images)
A model used by the Warren Commission to illustrate three shots allegedly taken by Lee Harvey Oswald is seen in the Sixth Floor Museum formally the site of the Texas School Book Depository October 8, 2013 in Dallas, Texas. The the Warren Commission, established by President Lyndon Johnson, studied and rep leased an official report on the assassination of US President John F. Kennedy. November 22 will mark the 50th anniversary of the assassination of JFK in Dallas's Dealey Plaza. AFP PHOTO/Brendan SMIALOWSKI (Photo credit should read BRENDAN SMIALOWSKI/AFP/Getty Images)
Lee Harvey Oswald (1939 - 1963) (C) is taken into custody by police after allegedly shooting President John F Kennedy, Dallas, Texas. (Photo by Archive Photos/Getty Images)
A map of Oak Cliff in Dallas, showing the location of eyewitnesses to the movements of Lee Harvey Oswald in the vicinity of the killing of police officer J. D. Tippit, 22nd November 1963. Tippit was shot by Oswald whilst attempting to bring him in for questioning in relation to the assassination of President John F. Kennedy. (Photo by Central Press/Hulton Archive/Getty Images)
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Thousands of books, articles, TV shows and films have explored the idea that Kennedy's assassination was the result of an elaborate conspiracy. None have produced conclusive proof that Oswald, who was shot dead a day after killing Kennedy, worked with anyone else, though they retain a powerful cultural currency.
"My students are really skeptical that Oswald was the lone assassin," said Patrick Maney, a professor of history at Boston College. "It's hard to get our minds around this, that someone like a loner, a loser, could on his own have murdered Kennedy and changed the course of world history. But that's where the evidence is."
In 1992, Congress ordered that all records relating to the investigation into Kennedy's death should be open to the public, and set a final deadline of Oct. 26, 2017 for the entire set to be made public.
President Donald Trump on Saturday confirmed that he would allow the documents to be made public.
The documents to be released on Thursday will likely focus on efforts by the Central Intelligence Agency and Federal Bureau of Investigation to determine what contact Oswald had with spies from Cuba and the former Soviet Union on a trip to Mexico City in September 1963, experts said.
"There was a real concern that Oswald was maybe in league with the Soviet Union," Maney said.
Kennedy's assassination was the first in a string of politically motivated killings, including those of his brother Robert F. Kennedy and civil rights leader Martin Luther King Jr., that stunned the United States during the turbulent 1960s. He remains one of the most admired U.S. presidents. (Reporting by Scott Malone)
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Massachusetts, USA, 1950's, President of the United States of America John F, Kennedy pictured as a young man with his wife Jackie Kennedy (Jacqueline Bouvier) early in their marriage (Photo by Popperfoto/Getty Images)
Massachusetts, USA, 1950's, President of the United States of America John F, Kennedy pictured as a young man with his wife Jackie Kennedy at home (Photo by Popperfoto/Getty Images)
NEWPORT, RI - SEPTEMBER 12: John F. Kennedy and Jacqueline Kennedy outside St. Mary's Church after their wedding on September 12, 1953. (Photo by Charles F. McCormick/The Boston Globe via Getty Images)
UNSPECIFIED - CIRCA 1754: US President John Kennedy, President Charles de Gaulle and Jackie Kennedy in Paris at the Elysee Palace May 31, 1961 (Photo by Universal History Archive/Getty Images)
1956: Waiter clearing dishes fr. table in front of actor David Niven (3R) sitting next to Sen. Jack Kennedy's wife Jackie (2R) w. others dining at society gala sponsored by wife of US Amb. to Cuba, in the ballroom of the Waldorf Astoria Hotel. At the far left is Jackie's sister Caroline Lee Bouvier (later Canfield, Radziwill, and Ross). (Photo by Yale Joel/The LIFE Picture Collection/Getty Images)
March 25, 1958: Sen. Jack Kennedy cuddling his darling baby daughter Caroline who is smiling as her mom Jackie looks on in delight while relaxing on bed at home. (Photo by Ed Clark/The LIFE Picture Collection/Getty Images)
JULY 20: John F. Kennedy and Jacqueline Kennedy. (Photo by Charles McCormick/The Boston Globe via Getty Images)
Sen. Jack Kennedy slyly lending an ear to his wife Jackie's giddy whisper as they sit together at table during cocktail hour before dining at society gala sponsored by wife of US Amb. to Cuba, at the Waldorf Astoria Hotel. (Photo by Yale Joel/The LIFE Picture Collection/Getty Images)
American future First Lady Jacqueline Kennedy (1929 - 1994) and her daughter Caroline pause on the stairs of their vacation home and look back down, Hyannisport, Massachusetts, September 1960. Ms. Kenney wears a trenchcoat and a flower-print scarf over her hair while Caroline is dressed in a overalls. (Photo by Alfred Eisenstaedt/The LIFE Picture Collection/Getty Images)
Jackie Kennedy and friends, circa 1960s. (Photo by Fotosearch/Getty Images).
CIRCA 1960s: Former First Lady Jacqueline Kennedy enjoys herself at a picnic circa the 1960s. (Photo by Michael Ochs Archives/Getty Images)
DISTRICT OF COLUMBIA, UNITED STATES - 1961: President Kennedy (R) with First Lady Jackie (L) (in fur-trimmed suit designed by Oleg Cassini) at his inauguration. (Photo by Leonard McCombe/Life Magazine/The LIFE Picture Collection/Getty Images)
PARIS, FRANCE - UNSPECIFIED DATE: American president John and Jackie Kennedy at the American Embassy during 1961 in Paris, France. (Photo by S010/COLLECTION SALINGER/Gamma-Rapho via Getty Images)
The newly-elected President John Fitzgerald Kennedy with wife Jackie after giving the traditional acceptance speech. USA, November 1960 (Photo by Mondadori Portfolio via Getty Images)
Frank Sinatra escorting Jacqueline Kennedy to her box at a gala, held at the National Guard Armory in Washington DC, the night before the inauguration of President John F. Kennedy, 19th January 1961. The gala was staged by Sinatra to help pay off the campaign debts of Kennedy and the Democratic Party. (Photo by GAB Archive/Redferns)
Portrait of American First Lady Jacqueline Kennedy (1960 - 1999) in the Red Room of the White House, Washington DC, January 15, 1962. During the filming of a CBS News Special program called 'A Tour of the White House with Mrs. John F. Kennedy,' she stands in front of an Alfred Wordsworth Thompson painting of the Civil War battle at Balls Bluff, Virginia. (Photo by CBS Photo Archive/Getty Images)
The President and Mrs. Kennedy attend a White House Ceremony February 19, 1963. (Photo by National Archive/Newsmakers)
First Lady Jackie Kennedy speaks to a guest while attending a White House ceremony January 8, 1963 in Washington, DC. (Photo by National Archive/Newsmakers)
UNITED STATES : A contemporary report ran: ?Caroline, five, moves into the big time. Big day for a small girl. The day she moved from the junior to the senior class. The day she rode not her own pony, Macaroni, but mother?s horse, Rufus, with her mother. The girl is Caroline Kennedy, five-year-old daughter of America?s President John Kennedy and his wife Jacqueline.? President Kennedy was assassinated later that year, on November 22. (Photo by SSPL/Getty Images)
18th October 1968: Millionaire shipping magnate Aristotle Onassis (1906 - 1975) with his wife Jackie (Bouvier Kennedy, 1929 - 1994). (Photo by Central Press/Getty Images)
Jackie Kennedy Onassis, Caroline Kennedy (left), John F. Kennedy, Jr., and Lee Rodziwill (Photo by Ron Galella/WireImage)
Jackie Onassis, Anthony Radziwill, and Tina Radziwill (Photo by Ron Galella/WireImage)
Jackie Onassis during Jackie Kennedy and Family Shopping in Capri - August 24, 1970 in Capri, Italy. (Photo by Ron Galella/WireImage)
Jackie Kennedy Onassis in Capri, Italy. (Photo by Ron Galella/WireImage)
Jackie Onassis (Photo by Ron Galella/WireImage)
Jackie Onassis with son John Kennedy Jr during Jackie Onassis Sighting at the Philharmonic Hall - December 13, 1971 at The Philharmonic Hall in New York City, United States. (Photo by Tom Wargacki/WireImage)
Washington, D.C. May 14th 1976. Jackie Onassis and Alexandrje Orfila at The Kennedy Center (Photo by Tom Wargacki/WireImage)
Jackie Onassis and Alex Orfila during OAS Party following the Kennedy Center Gala at Kennedy Center in Washington D.C., United States. (Photo by Ron Galella/WireImage)