From the article some of you are too lazy to read....
"If I were a real contestant, Nick would be working from a list of 50 questions painstakingly mined from my psychological profile and interviews with my relatives, friends and enemies. And here's the part I hadn't realized: Whenever anyone is asked a question on the air, no matter how shocking it may seem, they have already answered it. Twice.
On average, producers do the polygraph exam two to three weeks before the show tapes. Nick and the producers conduct a pretest exam before the machine is hooked up and then ask the exact same question, word for word, with the polygraph turned on. The query is then repeated — verbatim — on the show. Assuming you're willing to answer truthfully every time, The Moment of Truth is like an open-book exam."