WASHINGTON — Prosecutors and a defense lawyer recommend starkly opposing views on Friday in closing arguments for the politically charged trial of Michael Sussmann, a cybersecurity lawyer with ties to Hillary Clinton’s 2016 presidential campaign.
The case against Mr. Sussmann involves a narrow charge — an accusation of lying to the F.B.I. in a 2016 meeting — but is freighted with partisan overtones. Additionally it is a test of the special counsel who brought it, John H. Durham, since it is his first case to go to trial since he was appointed three years ago to scour the Trump-Russia investigation for any wrongdoing.
Two prosecutors told a jury that there was little doubt that Mr. Sussmann had lied to the F.B.I. to hide his clients — including the Clinton campaign — on the September 2016 meeting, which focused on suspicious data that cybersecurity experts said suggested the potential for a covert communications channel between Russia and someone near Donald J. Trump.
“It wasn’t about national security,” said one in all the prosecutors, Jonathan Algor. “It was about promoting opposition research against the opposition candidate — Donald Trump.”
But a defense lawyer, Sean M. Berkowitz, portrayed the case as riddled with uncertainties — including about what Mr. Sussmann actually said, whether it was false and whether it mattered if he was there on behalf of clients for the reason that F.B.I. would have investigated the tip regardless. Each was a path to seek out reasonable doubt and vote to acquit, he said.
“Mr. Sussmann’s liberty is at stake,” he said. “The time for political conspiracy theories is over. The time to speak concerning the evidence is now.”
A verdict is predicted as early as Tuesday.
The case centers on odd web data that cybersecurity researchers discovered in 2016 after it became public that Russia had hacked Democrats and Mr. Trump encouraged the country to hack Mrs. 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 researchers began working with Rodney Joffe, a technology executive who was an authority within the form of web data they were scrutinizing. Mr. Joffe brought the suspicions to Mr. Sussmann, who on the time represented the Democratic National Committee on matters related to Russia’s hacking of its emails. A partner at Mr. Sussmann’s law firm, Marc Elias, was the Clinton campaign’s general counsel.
Mr. Sussmann and Mr. Joffe tried to get reporters — including Eric Lichtblau, then of The Recent York Times — to write down concerning the matter, arguments within the trial showed. Mr. Sussmann continued to tell Mr. Elias about those efforts and discussed the matter with an opposition research firm the Clinton campaign had hired through Mr. Elias called Fusion GPS; the firm drafted a paper about Alfa Bank’s Kremlin ties that Mr. Sussmann later gave the F.B.I.
Mr. Sussmann logged those efforts in law firm billing records as time spent working for the Clinton campaign, Mr. Durham discovered.
On Sept. 18, 2016, soon after receiving an email claiming that Mr. Trump was upset a couple of Russia-related article that was soon to be published, Mr. Sussmann texted James A. Baker, the F.B.I.’s general counsel, and asked for a gathering the subsequent day. He indicated that he was coming not on behalf of any client, but to assist the F.B.I.
Mr. Durham’s team has accused Mr. Sussmann of constructing the identical claim when he met the subsequent day with Mr. Baker. In point of fact, prosecutors argue, Mr. Sussmann was concealing two of his clients — Mr. Joffe and the Clinton campaign.
Mr. Algor told the jury on Friday that the trouble was a conspiracy to engineer an “October surprise,” meaning a game-changing revelation late in a campaign, by getting the F.B.I. to open an investigation so reporters would write about it.
The F.B.I. — which had already opened its investigation scrutinizing possible ties between associates of Mr. Trump and Russia on other grounds — briefly checked out the Alfa Bank suspicions and quickly dismissed them.
In late October, Slate published an article concerning the matter, but it surely didn’t mention any F.B.I. investigation. That very same day, The Times published an article co-written by Mr. Lichtblau that mentioned the Alfa Bank suspicions but reported that the F.B.I. had to date found no conclusive or direct link between Mr. Trump and the Russian government.
The closing arguments focused on whether Mr. Sussmann repeated what he had said in his text message to Mr. Baker at their meeting the subsequent day — a vital technicality, because he’s charged just for what he purportedly said on the meeting itself.
Mr. Algor and one other prosecutor, Andrew DeFilippis, told the jury that the evidence left little doubt that Mr. Sussmann repeated to Mr. Baker’s face that he was not there on behalf of any client.
But Mr. Berkowitz pointed to Mr. Baker’s various recollections of that meeting. And he noted that Mr. Durham had been investigating Mr. Baker for an unrelated offense but didn’t charge him, insinuating that the witness had an incentive to recollect what the prosecutor desired to hear: “It’s no wonder he delivered on the stand.”
Mr. Berkowitz also argued that it was true that Mr. Sussmann was not there on behalf of any client. While Mr. Sussmann had two clients with an interest in Alfa Bank, the defense lawyer said, Mr. Sussmann was not advocating that the F.B.I. take some step on their behalf — or any step in any respect.
Countering that concept, prosecutors emphasized that on Sept. 13, Mr. Sussmann purchased thumb drives at Staples that he later expensed to the Clinton campaign; on the Sept. 19 meeting, he gave thumb drives to the F.B.I. Mr. DeFilippis called that “damning evidence.”
Mr. Berkowitz mocked that evidence — a Staples receipt, he noted — saying it was a time when Mr. Sussmann was doing all types of labor for the campaign. He also emphasized that Mr. Sussmann had not expensed to the campaign his taxi rides for the F.B.I. meeting, nor had he logged an “F.B.I. meeting” in billing records, as was his practice for such meetings.
And Mr. Berkowitz cited testimony by Mr. Elias and Mrs. Clinton’s campaign manager, Robby Mook, that they didn’t direct or authorize Mr. Sussmann to go to the F.B.I. and didn’t see that step as within the interest of the campaign. They testified that they’d just wanted The Times to publish an article; Mr. Baker testified that the F.B.I. asked Mr. Lichtblau to carry off on publishing anything so it could investigate first.