Why lies fail and what behaviors betray a lie.

This chapter provides a theoretical analysis of why some lies fail while others succeed and presents a discussion of its implications for the design and interpretation of research on deception. New findings on the measurement of facial expression, body movement, voice and verbal behavior are reported which show that the combination of facial and vocal measures allows highly accurate identification of deceptive behavior. Other data show, however, that most people do not make use of the behavioral cues most relevant to detecting deception, but instead they depend upon those behaviors least valuable in the detection of deception.