Then why did three soviet spies pass them with flying colors?
Tell me the names of the spies and I might be able to answer your question. In at least one high profile case, the suspected spy repeatedly “flunked” polygraphs but nobody in internal security raised a red flag. In at least one other such case, the suspect had mastered techniques to minimize the ability of the polygraph to detect deception. This is a very rare ability that most of us can’t acquire.