John F. Sullivan was a polygraph examiner with the CIA for thirty-one years, during which time he conducted more tests than anyone in the history of the CIA's program. The lie detectors act as the Agency's gatekeepers, preventing foreign agents, unsuitable applicants, and employees guilty of misconduct from penetrating or harming the Agency. Here Sullivan describes his methods, emphasizing the importance of psychology and the examiners' skills in a successful polygraph program. Sullivan acknowledges that using the polygraph effectively is an art as much as a science, yet he convincingly...