WASHINGTON — Michael Sussmann, a distinguished cybersecurity lawyer with ties to Democrats, was acquitted on Tuesday of a felony charge that he lied to the F.B.I. about having no client in 2016 when he shared a tip about possible connections between Donald J. Trump and Russia.
The decision was a blow to the special counsel, John H. Durham, who was appointed by the Trump administration three years ago to scour the Trump-Russia investigation for any wrongdoing.
Mr. Durham expressed disappointment in the decision but said he respected the choice by the jury, which deliberated for about six hours.
“I also want to acknowledge and thank the investigators and the prosecution team for his or her dedicated efforts in in search of truth and justice on this case,” he said in an announcement.
The case centered on odd web data that cybersecurity researchers discovered in 2016 after it became public that Russia had hacked Democrats and Mr. Trump had encouraged the country to focus on Hillary Clinton’s emails.
The researchers said the info might reflect a covert communications channel using servers for the Trump Organization and Alfa Bank, a Kremlin-linked bank. The F.B.I. briefly checked out the suspicions and dismissed them.
On Sept. 19, 2016, Mr. Sussmann brought those suspicions to a senior F.B.I. official. Prosecutors accused him of falsely telling the official that he was not there on behalf of any client, concealing that he was the truth is working for each Mrs. Clinton’s campaign and a technology executive who had brought him the tip.
Mr. Durham and his trial team used court filings and trial testimony to detail how Mr. Sussmann, while working for a Democratic-linked law firm and logging his time to the Clinton campaign, had been attempting to get reporters to write down concerning the Alfa Bank suspicions.
But trying to influence reporters to write down about such suspicions isn’t against the law. Mr. Sussmann’s guilt or innocence turned on a narrow issue: whether he made a false statement to a senior F.B.I. official on the 2016 meeting, by saying he was sharing those suspicions on behalf of nobody but himself.
Mr. Durham used the case to recommend a bigger conspiracy: that there was a joint enterprise to essentially frame Mr. Trump for collusion with Russia by getting the F.B.I. to research the suspicions so reporters would write about it — a scheme involving the Clinton campaign; its opposition research firm, Fusion GPS; Mr. Sussmann; and a cybersecurity expert who brought the odd data and evaluation to him.
That insinuation thrilled supporters of Mr. Trump who share his view that the Russia investigation was a “hoax,” and have sought to conflate the actual inquiry with sometimes thin or dubious allegations. In point of fact, the Alfa Bank matter was a sideshow: The F.B.I. had already opened its inquiry on other grounds before Mr. Sussmann passed on the tip, and the ultimate report by the special counsel, Robert S. Mueller III, made no mention of the Alfa Bank suspicions.
However the case Mr. Durham and his team used to drift their broad insinuations was thin — one count of constructing a false statement in a gathering with no other witnesses or contemporaneous notes. The evidence and arguments the lead prosecutor, Andrew DeFilippis, and his colleagues marshaled fell flat with the 12 jurors, who voted unanimously to search out Mr. Sussmann not guilty.
Some supporters of Mr. Trump had been bracing for that final result, pointing to the District of Columbia’s repute as a heavily Democratic area and affirming the prospect that a jury may be politically biased against a Trump-era prosecutor attempting to convict a defendant who was working for the Clinton campaign.
The judge told the jury that they weren’t to take any of their very own political beliefs under consideration when deciding the facts.
The defense, which portrayed prosecutors’ insinuations as “political conspiracy theories,” had argued that Mr. Sussmann only brought the matter to the F.B.I. when he thought The Latest York Times was already on the cusp of writing an article concerning the matter, to present the bureau a heads-up so it could not be caught flat-footed.
Clinton campaign officials testified through the trial that they had not told or authorized him to go to the F.B.I. — and that doing so was against their interests because they didn’t trust the bureau and it could decelerate the publication of any article.
This story is developing. Check back for updates.