Koecher, 51, and his wife, 41, came to the United States 20 years ago as Czech defectors. Actually, he had been trained for two years in Czechoslovakia as an intelligence officer and "successfully penetrated" the CIA, according to a court complaint filed by the FBI.
For 2 1/2 years - from February 1973 to August 1975 - he worked as a translator and consultant for the CIA, passing "virtually any" classified materials he was able to obtain, the complaint said.
The government contended that Hana Koecher was his courier, carrying the secret information to Czech agents in Europe. But she was not charged with any crime.
Instead, she was held as a material witness to appear before a grand jury. However, she refused to answer any questions, asserting a wife's privilege not to testify against her husband.
The case presented the issue of whether that privilege applies when there is evidence that the husband and wife were partners in crime.
A federal district judge said the privilege did not apply and ordered her to jail. But the U.S. Court of Appeals in New York disagreed and released her, citing "the harmony and sanctity of the marital relationship" and the ''natural repugnance in every fair-minded person to compelling a wife or husband to be the means of the other's condemnation."
The government appealed to the Supreme Court. The case was argued Jan. 15 and a final ruling was expected in the spring. But lawyers on both sides said that if the U.S.-Soviet swap occurs as planned, the case would become moot.
The Koechers, who have been married for almost 22 years, had lived since 1976 in a 32-story luxury cooperative apartment building in Manhattan. Among the tenants were tennis star Ivan Lendl, comedy filmmaker Mel Brooks and his wife, actress Anne Bancroft.
Koecher served on the co-op's board of directors and, according to one report, once sought to bar Lendl as a Czech "communist."
Koecher and his wife were arrested Nov. 27, 1984, after they had sold their apartment and hours before they were about to depart for Zurich, Switzerland, en route to Vienna, Austria. Koecher had contended that he was a ''double agent" who feigned disloyalty to the United States and passed false information to Czechoslovakia.
But his guilty plea makes him and Larry Wu-Tai Chin, who was convicted Friday in Alexandria, Va., of spying for China, the only two communist agents to have been apprehended after infiltrating the CIA.
In addition to the Koechers, the other spies to be released, West German government sources said, are:
* Yevgeny Zemliakov, 39, a former member of the Soviet trade mission in Cologne, West Germany, who was jailed for three years in September 1985 for high-technology espionage for Moscow.
* Jerzy Kaczemarek, 34, a lieutenant colonel in Polish intelligence, who was arrested in Bremen, West Germany, in March 1985 and was awaiting trial on charges of espionage in several cities since his arrival in West Germany in 1978.
* Detlev Scharfenorth, 43, an East German jailed in June 1985 in West Germany for a four-year sentence for economic espionage for East Germany's secret service, the Ministry for State Security.