Ana Montes, absolutely guilty of spying, evidence was Bountiful in her apartment yet Ana passed every polygraph test given to her. How? There are some physical things that you can do which can alter your physiology just enough during questioning & will cause the polygraphed to have a false reading.
https://en.m.wikipedia.org/wiki/Ana_Montes
Lots of proof like that which is why it’s inadmissible.