Paul Whelan, a former U.S. Marine serving a 16-year sentence in a Russian penal colony on espionage charges, did not figure in a prisoner exchange on Thursday involving U.S. basketball star Brittney Griner, despite months of speculation that he would be included.

Here are some facts about Whelan:

– Whelan was detained by agents from Russia’s Federal Security Service (FSB) in a room in Moscow’s Metropol Hotel, near the Kremlin, on Dec. 28, 2018.

– Investigators said he was a spy for military intelligence with a rank of colonel or higher, and had been caught red-handed with a computer flash drive containing classified information.

– Whelan said he had been in Russia for a friend’s wedding and had been given the drive in a sting by a Russian friend. He said he had thought it contained holiday photos.

– After a trial held entirely behind closed doors that U.S. diplomats said was unfair and opaque, Whelan, now 52, was convicted of spying in 2020, and sentenced to 16 years in a maximum security jail. He is currently being held in the IK-17 penal colony in the Mordovia region, east of Moscow.

– Born in Ottawa, Canada, to British parents of Irish origin, Whelan later moved to Novi, Michigan, and is a national of all four countries.

– Whelan served with the Marine Corps Reserve from 2003-2008, much of the time as an administrative clerk in Iraq. At the end of that period, he was dishonourably discharged for larceny and other lesser offences, after being found to have tried to steal $10,000.

– At the time of his arrest, Whelan was head of global security for BorgWarner, a Michigan car parts supplier.

– Last November, a Russian court rejected his request to be allowed to serve his sentence in the United States.