Layered Voice Analysis (VLA) is technology that records psycho physiological stress responses in a human voice. A person suffers psychological stress when under pressure, i.e. when being asked a question that instils fear of exposure. The consequences of lying and being exposed triggers a ‘high stress’ voice signature which the layered voice analyzer then records. Many intelligence agencies as well as private forensic psycho physiologists worldwide utilise layered voice analysis in preference to polygraph technology.