So what, they are about as accurate as a fortune teller if you ask me. They may get lucky and get it right every now and then.
You need to do some serious research into polygraph testing, how it works and how the tests are conducted.
This isn't a guy sitting in a room, asking questions and making up his mind by the manner a suspect answers a questions. It's based completely on biological factors, psychological factors that very few humans have control over.
It's obvious you know not the first thing about polygraphs or else you'd realize how ridiculous your comment is.