The success rate up to 90% claimed for lie detectors is misleadingly attractive. If we refer a figure to a company with 500 employees, twenty of are thieves, the lie detector could catch 18 of them, but in so would place 32 innocent employees suspicion. The problem for the management would therefore become of deciding much industrial unrest they prepared to cause in to eliminate theft. It seems surprising that a more effective way of using lie detectors has not into fashion. This method consists in the subject to read aloud statements about the crime question. Clearly, anyone who was not of the true facts would not any distinction between saying: 'The thief was a sports jacket' and 'The thief was dressed a blue suit'. a person who knew the true facts would be likely to register a reaction. or not he to disguise his reaction, the method would ensure that an innocent person could not be convicted in his place.