Plausible deniability
1. Plausible deniability is a political doctrine originally developed in the United States of America in the 1950s and applied to operations by the then newly-formed Central Intelligence Agency.Plausible deniability involves the creation of power structures and chains of command loose and informal enough to be denied if necessary. The idea was that the CIA (and, later, other bodies) could be given controversial instructions by powerful figures -- up to and including the president himself -- but that the existence and true source of those instructions could be denied if necessary; if, for example, an operation went disastrously wrong and it was necessary for the administration to disclaim responsibility.
The doctrine had two major flaws. First, it was an open door to the abuse of authority; it required that the bodies in question could be said to have acted independently, which in the end was tantamount to giving them license to act independently. Second, it rarely worked when invoked; the denials made were rarely plausible and were generally seen through by both the media and the populace. One aspect of the Watergate crisis is the repeated failure of the doctrine of plausible deniability, which the administration repeatedly attempted to use to stop the scandal affecting President Nixon and his aides.
2. Plausible Deniability has come to be used more generally to describe a situation in which a party actively avoids gaining certain, or confirmable, knowledge of facts it suspects to exist because it benefits the party to "not know." Example: An unscrupulous attorney may suspect that facts exist which would hurt his case, but decide not to investigate the issue because if the attorney had actual knowledge, the rules of ethics might require him to reveal those facts to the opposing side. Thus his failure to investigate maintains Plausible Deniability.