Charles McGonigal, who led the counterintelligence division of the FBI’s New York field office from 2016 through his retirement in 2018, admitted in August to working for Deripaska between spring and autumn of 2021 to find negative information on rival Russian oligarch Vladimir Potanin.

US district judge Jennifer Rearden imposed the 50-month sentence at a hearing in federal court in Manhattan.

Federal prosecutors in Manhattan had suggested Rearden sentence McGonigal to five years in prison, the maximum allowable for the one count of conspiracy to violate sanctions to which he pleaded guilty.

“McGonigal abused the skills and influence his country entrusted him with by secretly working for the very threats he had previously protected it against,” prosecutors wrote in a Dec 7 court filing. “No one knew better the gravity of McGonigal’s crimes than McGonigal himself.”

McGonigal’s lawyers said he should be spared prison time, arguing he had accepted responsibility and had already lost his job. They also said he thought his work for Deripaska was “consistent” with US foreign policy because it was in furtherance of potentially sanctioning Potanin.

Deripaska, the founder of Russian aluminum company Rusal, was among two dozen Russian businessmen and government officials on whom Washington imposed sanctions in 2018 in reaction to Russia’s purported meddling in the 2016 US election.

A lawyer for Deripaska, who has separately been charged with evading US sanctions, declined to comment.

The Treasury department sanctioned Potanin, the largest shareholder of metals producer Nornickel, in December 2022 as part of its push to pressure Moscow over its war in Ukraine.

McGonigal has separately pleaded guilty to a federal charge in Washington of concealing US$225,000 in cash payments from a former Albanian intelligence officer. He is scheduled to be sentenced on those charges on Feb 16.