A Russian military court on Monday handed down a 25-year sentence to a former senior intelligence officer for exposing 10 agents who were spying on the United States.

Colonel Alexander Poteyev was found guilty in absentia of high treason and desertion for betraying the so-called “sleeper cell” network whose agents posed as American professionals in order to gain access to advanced technologies and sensitive information.

Poteyev is believed to be living in the United States after fleeing Moscow by night train on word that the agents were being rounded up in June of last year. He left his wife behind and in a mobile phone message read to the court he told her, “I am leaving not for some time, but forever.”

The spy ring included red-head Anna Chapman who on her arrest become something of a media sensation. She and the other agents were deported in exchange for four Westerners jailed in Russia on suspicion of spying. It was the biggest spy swap since the Cold War.

Security analysts say the detection of the cell delivered a major blow to Russia's foreign intelligence efforts by revealing weaknesses in its surveillance program that had been the pride of the Kremlin since Soviet times.