Over the years, the history has recorded several attempts of both theoretical and graphical structuring of special knowledge applied in the criminal process. Contemporary doctrine recognizes a structural evolution of the category since the beginning of XX sec. The proposed constructions are delimiting the area of special knowledge of other type of knowledge through object, characteristics, research methodology etc. According to the general aspect, the model itself includes a three-dimensional structure: the informational level; the functional level; the normative-technical level. Thus, the specific contextual items for measuring and understanding special knowledge serve to measure the professional competence’ features of those skilled in applying special knowledge (specialist / expert).