Overview
Arguably, the key concept of plausible deniability is plausibility. It is fairly easy for a government official to issue a blanket denial of an action, and it is possible to destroy or cover up evidence after the fact, and this might be sufficient to avoid a criminal prosecution, for instance. However, the public might well disbelieve the denial, particularly if there is strong circumstantial evidence, or if the action is believed to be so unlikely that the only possible explanation is that the denial is false.
The concept is even more important in espionage. Intelligence may come from many sources, including human sources. The exposure of information to which only a few people are privileged may directly implicate some of those people in the exposure. Take for example a scenario where an official is travelling secretly and only one of his aides knows the specific travel plans. The official is assassinated during his travels, and the circumstances of the assassination strongly suggest that the assassin had foreknowledge of the official's travel plans. The probable conclusion is that the official has been betrayed by his aide. There may be no direct evidence linking the aide to the assassin, but collaboration can be inferred on the facts alone, thus making the aide's denial implausible.
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