The Moment Of Truth

Have you supported any country other than the U.S.?

Are you prejudiced?

Have you ever been the focus of a criminal investigation?

What do you think the worst thing you've ever done in your life is?

Polygraph testing has long been called "quackery" or "pseudo-science" by many scientists as well as by burned test-takers. In 1988, Congress outlawed the use of polygraph exams by employers in the private sector amid concerns about unwarranted invasions of privacy and the potential for false but potentially ruinous indications of deception.

Nevertheless, polygraph testing has remained legal in the public sector and is on the rise among federal agencies and local police departments, which rely on them to screen applicants and monitor the activities of their employees, said W.E. Chittenden, president of the Virginia Polygraph Association.

"We don't use it as a sole source of ruling someone out. It's just another tool to help qualify and rank candidates," said Leesburg police Lt. Jeff Dube, who is responsible for the department's hiring and recruitment.

Lest Mangan have any doubts about the test's accuracy, DeBow set up a drill. After hooking Mangan up with the chest straps -- pneumographs -- the blood pressure cuff and the fingertip clips, DeBow asked the applicant to pick a numbered card and lie when DeBow guessed the correct number. Judging from the spikes on the on-screen chart, DeBow correctly identified the number Mangan picked and then denied plucking.

Mangan looked impressed. Then he looked nervous. The real test was about to begin. DeBow ran through a list of questions he was going to ask, then went through them again, this time for real:

Is your first name Lawrence? Yes.

Have you ever detected a serious undetected crime? No.

Have you ever committed a sexual crime you could have been arrested for? No.