Skripal, who held the rank of colonel, was involved in military intelligence, although the details of his work have been withheld. Some reports have speculated that he was associated with the FSB. According to Russian prosecutors, he began working for the United Kingdom's MI6 intelligence agency in the late 1990s, while serving in the Russian Ground Forces. He was reportedly paid a large sum of money for giving away the identities of a number of Russian agents.
In December 2004, Skripal was arrested. He was charged with "high treason in the form of espionage", and was convicted. Prosecutors initially argued for fifteen years in prison — Skripal was eventually sentenced to thirteen, in recognition of his poor health and the fact that he co-operated with investigators. The affair was not revealed to the public until after he was sentenced August 2006. Skripal's lawyers have appealed the sentence.
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- "Russian convicted spy colonel worked for Britain's MI6", rian.ru, accessed August 10, 2006.
- "Russian colonel jailed for spying", bbc.co.uk, accessed August 10, 2006.
- "Colonel convicted of spying for U.K. appeals verdict", rian.ru, accessed August 11, 2006.
- Russia and US preparing spy swap The Telegraph, 7 July 2010.
- Russian spies deported in exchange for four pardoned agents