In 1994, the FBI arrested Aldrich Ames for espionage. He was a CIA agent for 30 years; during nine of those he sold secrets to the Soviet Union. While pleased Ames was convicted, the agencies believed other agents were still spying.
The FBI compiled a list of secrets believed to have been stolen and began looking for agents with access to the leaked information. They reduced their list of potential spies from 100, to seven, and eventually to one, Brian Kelley. Despite the fact he was a highly respected CIA agent with five medals, the FBI was convinced he was guilty.
In 1997, Kelley was reassigned to CIA headquarters, which allowed the agencies to watch him and hopefully collect enough evidence to arrest him. They planted listening devices in his home, secretly searched it, tapped his phones and placed him under round-the-clock surveillance. The only suspicious evidence they found was a map of a local park where Soviet agents had been seen. They believed it was where he had left information for the KGB.
The FBI knew it did not have enough evidence to convict Kelley, so they offered an assignment which required him to take a polygraph test. To everyone’s surprise he easily passed.
After more attempts to get Kelley to incriminate himself, he was confronted by two FBI agents in 1999 who informed him they knew all about his spying and pushed him to confess. Kelley explained the map was merely a record of his jogging. He willingly answered questions for seven hours without an attorney present and even offered to take another polygraph test.