The article has discussed the issues relating to the involvement of a psychologist in conducting comprehensive psychological and linguistic investigations of texts. The theory of the linguistic and psychological content of legal concepts has been examined in the light of the traditional understanding of expert work. It has been argued that expert studies based on such a theory constitute legal decision-making rather than fact-finding through the use of specialized knowledge. The main problems that arise in the psychological and linguistic expertise in terms of identifying the purpose of the speech product and the outcome of the speech impact have been considered. The authors have questioned the validity of existing approaches to identifying the psychological components of the text (psychological orientation, social attitudes of the author and social attitudes formed in the addressee). The question has been raised as to the correlation between the psychological line of text and the intention and illocutionary purpose, as well as the correlation between the social attitudes formed in the addressee and the perlocutionary purpose and the actual result of the speech effect. According to the authors, both the fact of the existence of such psychological components of the text and the possibility of extracting them from the text by psychological methods require justification. The examples of effective interaction between a psychologist and a linguist in comprehensive expertise have been discussed in the article.