What's interesting though is that a failed polygraph reading isn't sufficient to charge someone with lying to investigators because they would have to prove a p

What's interesting though is that a failed polygraph reading isn't sufficient to charge someone with lying to investigators because they would have to prove a polygraph is correct beyond a reasonable doubt. Furthermore, they wouldn't ask you a question they already know the answer to. For example, if they ask you, have you ever done drugs in the past, you wouldn't be there if they already knew the answer was yes.