[1] As the son of an Anglophile, Koecher gained his language skills from an early age attending an English grammar school and later French lyceum before the war.

[1] He became a radio comedy writer and was allegedly frequently scrutinized by the Communist security forces for his satire that mocked the regime (this turned out to be a pre-planned "cover story").

[7] In 1965 he and his wife, Hana Koecher (the daughter of a Communist Party official),[8] seemingly emigrated to the United States via Austria posing as defecting dissidents.

[9][1] His language skills and status as a defector aided Koecher in gaining employment at Radio Free Europe and a year long fellowship at Indiana University.

[1] After several years as a sleeper he was hired by the CIA as a translator/analyst in 1973[9] due to his fake dissident credentials and skills in a number of Eastern European languages.

He was given high level security clearance and given the job of translating and analyzing documents handed over by CIA agents and transcripts of wiretaps and bugs.

[14] Another suggestion by a CIA historian, is that it was the StB intelligence officer, Jan Fila, who betrayed him with the latter disappearing in December 1989, a month after the Czechoslovakian Velvet Revolution.

[1] The FBI apprehended Koecher on 27 November 1984, outside New York City's Barbizon Plaza Hotel, and brought him and, soon afterwards, his wife Hana in for several days of questioning.

[citation needed] On November 27, 1984, the day after the couple sold their apartment[15] and hours before they were scheduled to fly to Switzerland, Koecher and his wife were arrested in New York City.

[15] The case on his wife, Hana, a purported diamond merchant but actually a courier for the StB from 1974 to 1983, had been bungled and would not result in a conviction, so the prosecutors allowed her to gain immunity in return for information against her husband Karl Koecher.

[21] Koecher, worrying about his own safety, sent through his lawyer and his spouse's father, a request to the KGB chairman that he be part of a prisoner exchange with the Soviets.

[d] Koecher pleaded guilty on charges of conspiracy to commit espionage for Czechoslovakia,[18] and was sentenced to life in prison,[19] which was reduced to time served provided he left the US and never returned.

[22] On February 11, 1986, Koecher and his wife were part of a nine-person exchange at Glienicke Bridge in Berlin, of which the most prominent member was noted dissident Anatoly Shcharansky.

His wife, Hana Koecher, made the headlines in the Czech Republic, when she was fired from her new job as a translator for the British Embassy in Prague.