The FBI decided, based on limited information from a KGB defector, that Colonel George Trofimoff had leaked classified information to the Soviets in the decade of the 70s.
It was a time when Col. Trofimoff was Chief of an interrogation center for the U.S. Army in Nurenberg, Germany. The FBI knew it had neither enough information to identify the spy the defector had referred to, nor enough knowledge about Trofimoff, himself. The only way to get such information would be to get Trofimoff to talk. The Agency decided to make this retired colonel in Florida a target and to set up a sting operation
They sent an agent who said he was from the Russian Embassy in D.C. who was trying to clear up some KGB leaks from the 70s. Without Trofimoff knowing it, they began monitoring his bank account and learned that he was debt-ridden on his house first and second mortages and credit cards. As Trofimoff tried, at the age of 72, to make outside income to pay on debt, he took on a job sacking groceries at the local Publix grocery. The FBI agent moved in on his target, worked on him for two years and offered Trofimoff $45,000, if he would meet with him and tell a story of KGB espionage and leaking classified documents.
I write of Colonel George Trofimoff in my book: “Observer: The Colonel George Trofimoff Story, the tale of America’s highest ranking military officer convicted of spying”