For some time, various scientific methods or devices have been promoted as foolproof ways of detecting criminal deception. Yet research and observation demonstrate that most of these methods or devices are not successful most of the time. To discover why this is so, research has concentrated on the beliefs and psychological traits of the deceivers and, sometimes, on the beliefs and psychological traits of the deception detectors. The findings of deception research however are contradictory and are continually being reevaluated by other research. This paper examines current deception research in terms of the constant reevaluation of previousresearch and the introduction of new variables and, in light of this scrutiny, focuses on the claims of Scientific Content Analysis (SCAN), a technique that is used by police in various countries to analyse written statements.