When it comes to detecting lies and deception, the more reliable information and training we have at our disposal, the more effective we will likely be. Based on several international studies, most people rely on eye movement to tell if someone is lying or not. The common belief is that when people look away - gaze aversion - they must be lying because "they couldn't look me in the eye!" Countless research studies failed to support this belief, and in fact, this belief is so widespread that many times the liar will make a point to look you dead in the eye, because he too believes if he looks away you may not believe his lie. This is called "impression management".
The video below is a short clip on micro expressions with Paul Ekman. By having good training with investigative interviewing and criminal interrogations, knowing what to look for and how to apply it within the contex of the interview, and adding skills like understanding and reading emotions and micro expressions in people will provide you with the much needed edge in your interviews and interrogations and assessments of truthfulness and deception in people.