A former assistant director for the FBI said Friday that authorities would not have gone to the trouble of extraditing a notorious Romanian hacker unless he was key to their investigation of Hillary Clinton.

Marcel Lehel Lazar, known online as “Guccifer,” was extradited from a Romanian prison at the end of March and relocated to a facility in Alexandria, Va. He is scheduled to remain in the country for 18 months while he faces a nine-count federal indictment on hacking charges.