I think many on this thread are missing the point. the fact that it had to be waived alone speaks volumes. Sure they're about as accurate as a coin flip as the top commenter said, but they are theatrics and what you do before, during, and after usually gives interrogators lots of clues about you that they wouldn't otherwise have observed.

If you're trying "tricks" to get past it for example, that's one data point. It's useful for things like clearance investigations because there is a counter-intel side to it, your comms, pattern of live and other things will be scrutinized.

it is essentially a "vibe" tool. Do you look too clam, too nervous,etc..

That said, people end up contradicting themselves when focusing too much on beating the polygraph too. Skilled interrogators throw questions that will cause that. Do you sound too prepared and detailed, answering questions with details most people won't remember? Are you too consistent, indicating recollection of prepared facts, instead of wading through unreliable human memory?

Even without a polygraph, your eye movements alone are hard to get under control unless you practice for it. That's why they baseline you first with simple things you're expected to lie on, and then more complex things that most people would at least partially lie about.

The accuracy of the polygraph itself is not too relevant. If you're hiring someone for a senior role at the FBI, a polygraph is the formality that opens you up to all kinds of legal trouble. it's purpose is to put the subject under legal jeopardy. A simple interrogation will do, but a polygraph introduces an adversarial evidentiary element into the equation.

In short, it gives the FBI in this case the option to say "this guy is acting shady, we can't trust him". Even if they're wrong, the sensitivity of the position requires passing on good candidates if they must. An investigator on their own would have to prove/justify their conclusion. a polygraph is their way out. They've seen spies, traitors, etc.. it's a way to filter people out with a somewhat justifiable cause.

The question you should be asking is why was it waived in this case just for those three staff members? If it is indeed unreliable, why not stop it entirely?

Millions of Americans have TS/SCI clearance, which had them pass a polygraph just fine. The government isn't losing a lot of talent who're fumbling a polygraph. This is a big deal. Any conversation about the reliability of a polygraph is a distraction.

It doesn't speak volumes. It just says that the people being hired had enough status that they don't have to go through what amounts to an initiation ritual.

Polygraphs appear to be another sad outcrop from the same pseudoscience formation as phrenology or witch-ducking; basically theatre to legitimise people exercising power in a way they were already going to do. The fact that it gets used speaks more volumes about the culture in intelligence services than the people who may or may not undergo the test.