The author draws attention to several determinants of relativism in forensic-psychological expertises. These include an excessive tendency towards statistical interpretation of test findings as well as errors due to the use of a diverse range of psychological instruments and methods lacking in terminological homogeneity. Among other errors he includes excessive focus on "organic" variables (results of organic tests, EEG, TC) as significant behaviour determinants. According to the author, more information for the explanation of illegal human behaviour can be gleaned from the analysis of the motivational process and especially those functions of this process which are formed by social norms and value networks, i.e., universal ones. One cannot infer the understanding of social norms and the essence of human bonds from psychological assessment. When analyzing human motivation the psychologist should take into account the widely conceived human problem and include the experience of other thought systems, e.g. ethics, religion and anthropology. In particular, he/she ought to monitor the effects of modern culture, life-styles, economic transformation on human behaviour and the reception of these phenomena by the young generation.