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circa 1945: American criminologist John Edgar Hoover (1895 - 1972), the Director of the FBI (Federal Bureau of Investigation) for 48 years. (Photo by MPI/Getty Images)

circa 1945:  American criminologist John Edgar Hoover (1895 - 1972), the Director of the FBI (Federal Bureau of Investigation) for 48 years.  (Photo by MPI/Getty Images)

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FBI director J. Edgar Hoover reviews weapons. (Photo by Jeffrey Markowitz/Sygma via Getty Images)

FBI director J. Edgar Hoover reviews weapons. (Photo by Jeffrey Markowitz/Sygma via Getty Images)

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1953: US Federal Bureau of Investigations (FBI) Director J Edgar Hoover sits at a table, speaking into several microphones. (Photo by Hulton Archive/Getty Images)

1953:  US Federal Bureau of Investigations (FBI) Director J Edgar Hoover sits at a table, speaking into several microphones.  (Photo by Hulton Archive/Getty Images)

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Director of the FBI John Edgar Hoover tests and aims a weapon. (Photo by Jeffrey Markowitz/Sygma via Getty Images)

Director of the FBI John Edgar Hoover tests and aims a weapon.  (Photo by Jeffrey Markowitz/Sygma via Getty Images)

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28th February 1961: American President John F Kennedy (1917 - 1963) at the White House with his brother Attorney General Robert Kennedy (1925 - 1968) and head of the FBI J Edgar Hoover (1895 - 1972). (Photo by Keystone/Getty Images)

28th February 1961:  American President John F Kennedy (1917 - 1963) at the White House with his brother Attorney General Robert Kennedy (1925 - 1968) and head of the FBI J Edgar Hoover  (1895 - 1972).  (Photo by Keystone/Getty Images)