A simple test.
A simple test for determining whether or not a Soviet or Russian Intelligence defector is fake is to ask him or her whether or not putative KGB staff officer Yuri Nosenko was a true defector-in-place in Geneva in June 1962 (he wasn’t), whether or not KGB Major Aleksei Kulak (aka FEDORA) was truly spying for the FBI’s NYC field office from 1962 to 1977 (he wasn’t), and whether or not KGB Colonel Vitaly “Homesick” Yurchenko truly defected to the U.S. in 1985 (he didn’t).
It’s also a good test to determine whether or not certain espionage writers are “useful idiots” or perhaps something worse.
Same for CIA officers whose views are known. Bruce Leonard Solie (R.I.P.), Leonard V. McCoy (R.I.P.), and Russia-born George Kisevalter (R.I.P.) come to mind.
Two “former” Russian spies who fail these tests miserably are Oleg Kalugin and Oleg Gordievsky.
Two writers who fail spectacularly are Tom Mangold and David Wise, the former more spectacularly than the latter.
To learn more about Nosenko, Kulak, Yurchenko, and GRU Lt. Col. Dmitry Polyakov (who flipped to the CIA after he left NYC in late 1962), et al., read Tennent H. Bagley’s 2007 Yale University Press book, Spy Wars, and his 2014 follow-up article “Ghosts of the Spy Wars.”
You can read them for free by googling “spy wars” and “archive” simultaneously and “ghosts of the spy wars” and “archive” simultaneously.