The Moment Of Truth

"Everybody has that deep, dark little secret that they want to keep hidden," DeBow said. His job is to expose buried misdeeds through his probing questions and, later, through his technological fluency.

The informal, introductory questions continued:

Did you ever commit the act of burglary?

Assault and battery? Domestic abuse?

Rape, forcing someone to have sex who was drunk or drugged?

Exposing yourself or peeping in someone's window?

Petty larceny; theft of anything?

After a string of no's, Mangan hesitated at the last question. The hum from the computer filled the room.

"I guess when I was a kid, maybe candy," Mangan finally said.

"When you lie, you have what is called a sympathetic response; your body goes into fight-or-flight mode," DeBow said. "It affects the pulse rate, blood pressure, respiratory and galvanic skin response [sweatiness]. We measure these things."

"That's nonsense," said Drew C. Richardson, a former FBI agent with a PhD in physiology. He has testified before the Senate, challenging the government's use of polygraph testing. "There isn't an isolated 'lie response,' " he said.

Such emotions as anger, surprise or revulsion also can trigger similar physiological responses, Richardson said. When a job is on the line, someone could be responding in fear "to the consequences of being branded a liar, rather than being caught in a lie," he said.