I was interested in a LEO job a few years back. I had looked at this website and read the material on the poly. I took the test and passed with no problem. 

The test consisted of about a hundred questions between the interviewer and myself, mainly covering areas of drugs, theft, sex, violence, and the like. After the interview questions, he put an arm cuff on, and a clip on my finger. Then it was pretty simple from there, all he asked me was a few questions (what is your name, are the lights on, etc. and then told me to lie on one question). Then, he simply asked "regarding section 1, were you deceptive in any part of it?" And he asked the same question for section 2, 3, etc. and that was it. He said "you did fine" we BS'd about some sports, and I was out the door.

But that got me thinking, and my question is this. Say someone was a complete deviant. They were a violent person, stole from work, got into fights, weird sex, the whole 9. And this person takes the test and lies on everything, making himself out to be a saint.

When he gets to the end of the poly, where he is asked if he lied on any part of the test, he is going to say no I was truthful, for every section. The machine would not show him being deceptive, he would look normal as his readings would be the same across every question. It seems as though a "complete liar" would have any easy time passing the polygraph. In fact, the more lies you make, the more "normal" you would appear.

This is a very scary thought in my mind, what am I missing?

Thank you for the reply. 

Still wondering about this part though, it seems that the more lies one tells, the better their chances of passing?

"When he gets to the end of the poly, where he is asked if he lied on any part of the test, he is going to say no I was truthful, for every section. The machine would not show him being deceptive, he would look normal as his readings would be the same across every question. It seems as though a "complete liar" would have any easy time passing the polygraph. In fact, the more lies you make, the more "normal" you would appear."