Igor Danchenko, a consultant whose information comprised the bulk of the 2016 “Steele dossier,” was acquitted Tuesday of lying to the Federal Bureau of Investigation, leaving special counsel John Durham with losses in both cases he took to trial as his yearslong inquiry into the FBI investigation into Russian interference in the 2016 election winds down.

Over four days in federal court outside Washington, D.C., Mr. Durham sought to portray Mr. Danchenko as fabricating one of his own sources and concealing another one when the FBI questioned him in 2017 about where he obtained the allegations he provided to ex-British spy Christopher Steele, who was paid by Democratic operatives to collect opposition research on then-presidential candidate Donald Trump and alleged ties to the Kremlin. 

But several of Mr. Durham’s own FBI witnesses appeared to undercut his allegations and said they believed Mr. Danchenko had been truthful.

Mr. Steele gave the dossier to the FBI, whose efforts to verify what was in the memos included interviewing Mr. Danchenko. Much of what was in the document has since been discredited but its compilation, and how it was handled by the Federal Bureau of Investigation, became a central focus of Mr. Durham after he was appointed by then-Attorney General William Barr in 2019. Mr. Durham, a longtime federal prosecutor often tapped for sensitive investigations into government misconduct, was then the U.S. attorney for Connecticut. Mr. Durham spent parts of the trial criticizing decisions the FBI made in the Russia inquiry.