This paper substantiates the need to develop a new special theory of the use of expert knowledge in the framework of ensuring information and worldview security in the digital environment, aimed at analyzing and generalizing the possibilities of using a range of expert knowledge for the study of criminogenic information disseminated within the digital environment. For these purposes, conceptual frameworks have been developed, including the subject and the system of new expert theory, as well as other terms that are important for a holistic understanding of this area (such as "digital environment", "information (worldview) security", "value basis"). The involvement of persons with special knowledge is important due to the peculiarities of information disseminated in the digital environment (such as electronic form, hypertextuality, etc.). In this case, the question often arises about the need for a comprehensive expert analysis (for example, the use of special knowledge in the field of forensic speech and forensic psychology, special computer-technical knowledge, etc.). The result of the study is conclusion on the need to develop a new private expert theory; the paper defines its conceptual foundations in the form of a consideration of its subject and system.