Charlatanry in forensic speech science : A problem to be taken seriously

A lie detector which can reveal lie and deception in some automatic and perfectly reliable way is an old idea we have often met with in science fiction books and comic strips. This is all very well. It is when machines claimed to be lie detectors appear in the context of criminal investigations or security applications that we need to be concerned. In the present paper we will describe two types of ‘deception’ or ‘stress detectors’ (euphemisms to refer to what quite clearly are known as ‘lie detectors’). Both types of detection are claimed to be based on voice analysis but we found no scientific evidence to support the manufacturers’ claims. Indeed, our review of scientific studies will show that these machines perform at chance level when tested for reliability. Given such results and the absence of scientific support for the underlying principles it is justified to view the use of these machines as charlatanry and we argue that there are serious ethical and security reasons to demand that responsible authorities and institutions should not get involved in such practices. keywords: lie detector, charlatanry, voice stress analysis, psychological stress evaluator, microtremor, layered voice analysis, airport