According to historian Timothy Naftali, who has read recently declassified C.I.A. documents, the Agency knew from West German intelligence that Adolph Eichmann was living in Argentina, but did not share that information with Israel. According to a story in the New York Times:
The Eichmann papers are among 27,000 newly declassified pages released by the C.I.A. to the National Archives under Congressional pressure to make public files about former officials of Hitler's regime later used as American agents. The material reinforces the view that most former Nazis gave American intelligence little of value and in some cases proved to be damaging double agents for the Soviet K.G.B., according to historians and members of the government panel that has worked to open the long-secret files.
This prompted one panel member, Elizabeth Holtzman, a former New York congresswoman, to observe that the C.I.A "failed to lift a finger" to hunt Eichmann, which forced the United States "to confront not only the moral harm but the practical harm" of relying on intelligence from ex-Nazis.
The idea of using war criminals to get intelligence is hardly something a spy agency from a democratic country wants to highlight, and in Eichmann's case the C.I.A. apparently wanted to avoid his drawing attention to Hans Globke, a former Nazi government official then serving as a top national security adviser to Chancellor Konrad Adenauer.
However, placing the debate on the moral or practical level also poses problems: espionage sources are often the scum of the earth when it comes to personal ethics; does this mean intelligence agencies should not use them? And the fact, as Holtzman complained, that the Nazis were vulnerable to Soviet blackmail, hence were unreliable to the U.S., can be turned around: what prevented the Americans from blackmailing them back? The Nazis did good work for the U.S.S.R., so in principle a war criminal does not a bad spy make, if he can be properly squeezed by the other side.