If I remember correctly, note this is contrary to the advice the antipolygraph sites gives. They state anything the person interviewed admits, no matter how trivial, will be used against them (e.g. "have you ever smoked pot in college?"). That the "good cop" of the interrogation is always a ruse; and that since polygraphs don't actually work, small "admissions" are a big part of the actual information gathering... including the questions that are allegedly for "calibration".