FRONTLINE marks the 50th anniversary of John F. Kennedy's assassination with a reprise of its investigative biography of the man at the center of the political crime of the 20th century. At the heart of the assassination lies the puzzle of Lee Harvey Oswald: Was he the emotionally disturbed lone gunman of the 1964 Warren Commission report? Was he, as the House Select Committee on Assassinations concluded, probably part of a conspiracy on that day in Dallas? Or was he an unwitting fall guy, the patsy, as Oswald himself claimed when he was arrested on November 22, 1963? Twenty years ago, in the most comprehensive attempt on American television to penetrate this enduring enigma, FRONTLINE's investigative team spent more than a year reexamining Oswald's life and sifting through the psychological, political, and forensic evidence of his role in the assassination. Traveling to Japan, Russia, Europe, Mexico, Canada and across the United States, the team uncovered new witnesses, documents, photographs, video and audio recordings of Lee Oswald, many of which had never before been made public.