My uncle had to take one many years ago...and his attorney advised against it because they are not 100% accurate and what it shows, is solid evidence in a case (even though they all know they are not 100% accurate). Anyway, he knew that he was not guilty of whatever it was at the time (something petty, but I can't remember)...anyway, he wanted to prove to everyone that he was telling the truth....well, the test showed that he lied and it was then evidence in court. ---So...I would definitely talk to an attorney!
So scary...I've never had to have one, nor do I ever wish to be in a situation to take one!