The conference was optimistically titled "Cracking the JFK Case," but it was widely noted that many of the speakers and members of the audience had grown gray hair or lost much of it while looking for the answers.

One of the presentations at the three-day session revived doubts about the famous "single bullet theory" that the House Select Committee on Assassinations thought it had resolved in the late 1970s. Another demolished persistent claims that the Zapruder film -- the "clock" of the Kennedy assassination -- had somehow been altered or contradicted by other photographic evidence. Still another speaker demonstrated how the sounds on Dallas police tapes showed that four and perhaps five shots had been fired -- meaning that at least one other person besides alleged assassin Lee Harvey Oswald had squeezed a trigger.

None of that solved the whodunit, although the conferees could still count themselves and like-minded historians and researchers winners in a way. Three out of every four Americans think President John F. Kennedy's assassination on Nov. 22, 1963, was the result of a conspiracy. Almost as many think there was a coverup.

But the proposition that drew about 135 people to a Bethesda hotel this past weekend -- that it is not too late "to solve the greatest mystery of the 20th century" -- has less traction with the public. According to the most recent poll, conducted in 2003 for the 40th anniversary of the JFK assassination, 75 percent of the public does not want another government investigation.

Washington lawyer Jim Lesar, president of the nonprofit Assassination Archives and Research Center, the main sponsor of the conference, was undeterred. "The lone assassin theory" -- the Warren Commission's conclusion in 1964 that Oswald was solely responsible for the killing -- "is more discredited than it has previously been," he said in opening remarks.

A key reason, he said, is that the CIA not only withheld crucial information from the commission about its assassination plots against Cuban President Fidel Castro and other foreign leaders, but it also held back other vital information from the House assassinations committee, which concluded in 1979 that Kennedy was "probably assassinated as a result of a conspiracy."