The special counsel appointed by the Trump administration to scrutinize the Russia investigation obtained a grand jury indictment on Thursday of a prominent cybersecurity lawyer, accusing him of lying to the F.B.I. five years ago during a meeting about Donald J. Trump and Russia.
The indictment secured by the special counsel, John H. Durham, also made public his findings about an episode in which cybersecurity researchers identified unusual internet data in 2016 that they said suggested the possibility of a covert communications channel between the Trump Organization and Alfa Bank, a Kremlin-linked financial institution.
He concluded that the Clinton campaign covertly helped push those suspicions to the F.B.I. and reporters, the indictment shows. The F.B.I. looked into the questions about Alfa Bank but dismissed them as unfounded, and the special counsel who later took over the Russia investigation, Robert S. Mueller III, ignored the matter in his final report.
The charging of the lawyer, Michael A. Sussmann, had been expected. He is accused of falsely telling a top F.B.I. lawyer that he was not representing any client at the meeting about those suspicions. Prosecutors contend that he was instead representing both a technology executive and the Hillary Clinton campaign.
“Sussmann’s false statement misled the F.B.I. general counsel and other F.B.I. personnel concerning the political nature of his work and deprived the F.B.I. of information that might have permitted it more fully to assess and uncover the origins of the relevant data and technical analysis, including the identities and motivations of Sussmann’s clients,” the indictment said.
Mr. Sussmann’s defense lawyers, Sean Berkowitz and Michael Bosworth, have denied the accusation, insisting that he did not say he had no client and maintaining that the evidence against him is weak. They also denied that the question of who Mr. Sussmann was working for was material, saying the FB.I. would have investigated the matter regardless.