The polygraph and forensic psychiatry.

The Blue Fairy in Pinocchio stated confidently, “Lies can be easily recognized. There are two kinds of them: those with short legs, and those with long noses” (Ref. 1, p 89). While perhaps true for her, the Blue Fairy was wrong when it comes to humans, who are in general poor lie detectors. In experimental settings, the ability of the average person to catch a liar is typically little more than chance and rarely above 60 percent. So-called professional lie catchers do not do much better, at least in laboratory studies: police officers, customs agents, American federal law enforcement officials, and judges are no more accurate than university students in detecting deceit in experimental settings. Secret Service agents appear to perform somewhat better, but even they get it right only two of three times. It is unlikely that forensic psychiatrists differ much from anyone else in having only a limited ability to differentiate truth-telling from deception. Barring the occasional minimization and exaggeration, most doctors and most psychiatrists believe what their patients tell them, most of the time. Forensic psychiatrists, however, typically maintain a higher degree of skepticism than do other doctors. We do not, of course, call our patients liars, but a lack of honesty can present significant obstacles to assessment and treatment. In some situations, for example in criminal proceedings or compensation claims, patients may attempt to present themselves as much worse than they are; in others, for instance when seeking release from a forensic institution or avoiding recall to one, they may deny the extent of their symptoms or behavior. Forensic psychiatrists are therefore advised to make use of multiple sources, and if possible extended observation, to detect deception. In addition, scales to identify malingering are sometimes advocated, and many psychometric tests contain what amounts to a lie scale. Given this mindset, why then is so little consideration given to the use of what is probably the most quintessential approach to detecting lies—the polygraph? The suggestion that we might use polygraphy to detect deception (or confirm honesty) in patients typically elicits an instinctive and immediate rejection, based on the assumption that it will have a negative impact on the therapeutic relationship or is in some way unethical. After all, who likes to be called a liar, even when he is lying? In addition, polygraphy is associated with a fair amount of controversy, and there is a widespread belief that it can be easily beaten or that it “doesn’t work” and has been “discredited.” Much of the debate around polygraphy is colored by ideology, with both proponents and antagonists often overstating their cases. With the froth trimmed off and used appropriately, might there be a role for polygraph testing in the assessment and treatment of forensic patients?