Gaeton Fonzi was one of the most relentless investigators on the House Select Committee on Assassinations in the late 1970s, remembered by former colleagues with [awe at] his pursuit of the full story behind the assassination of President John F. Kennedy. Mr. Fonzi was also the staff member most publicly dismayed by the committee's final report, which concluded in 1979 that the president was probably assassinated as a result of a conspiracy." Of course it was a conspiracy, said Mr. Fonzi, a journalist recruited mainly on the strength of scathing magazine critiques he had written about the Warren Commission and its conclusion that Lee Harvey Oswald had acted alone in killing the president in Dallas on Nov. 22, 1963. But who were the conspirators? What was their motive? How could the committee close its doors without the answers? Mr. Fonzi ... nailed those questions to the committee's locked doors, figuratively, in a long article he wrote the next year for Washingtonian magazine and in a 1993 book, The Last Investigation. In both, he chronicled the near-blanket refusal of government intelligence agencies, especially the C.I.A., to provide the committee with documents it requested. And he accused committee leaders of folding under pressure - from Congressional budget hawks, political advisers and the intelligence agencies themselves - just as promising new leads were emerging. "Is it unrealistic to desire, for something as important as the assassination of a president, an investigation unbound by political, financial or time restrictions?" he asked.