Introduction: the author examines the factors that enhance the efficacy of legal assistance in criminal cases, identifies concerns and features in a preliminary investigation when international cooperation of law enforcement agencies is required, and elucidates the primary reasons for the incompatibility between domestic law and international law. In light of the findings of the study, the author puts forth suggestions for future development in this field and recommendations for enhancing the efficacy of the preliminary investigation body. Materials and Methods: the study was based on an analysis of international treaties and agreements, regulatory acts, and the proceeding papers of the subject. The author employed a dialectical, comparative legal and legal methodology. Results: the findings indicate that international legal instruments regulating legal assistance in criminal cases are comprehensive in nature. However, an analysis of the legal acts suggests that this area is not without shortcomings and requires comprehensive and coherent enhancement. Furthermore, there is a discrepancy between the practices of law enforcement in international criminal proceedings and the realities of the modern world. To address these shortcomings, the author proposes that Russian education should be oriented towards training specialists who meet the demands of the contemporary era. The author suggests the introduction of specialized courses in foreign criminal law and procedural law. Discussion and Conclusions: it is imperative that a codification of mutual legal assistance be established. Domestic codification is feasible through the enactment of a specific law or the amendment of existing criminal and criminal procedural legislation. The author's perspective is that the enactment is a more preferable course of action for the Russian Federation. In order to enhance the efficiency and efficacy of the investigative work conducted by the Ministry of Internal Affairs of the Russian Federation, it is essential to implement measures that facilitate international cooperation. 1. It is imperative to guarantee precise adherence to the stipulations set forth in regulatory documents. 2. It is imperative to establish personal accountability of the pertinent managerial personnel for the organisation of work in this domain. 3. It is recommended that additional training be conducted within the framework of the official training programme, with the adoption of credits for the study of international cooperation norms and the criminal procedure legislation of the Russian Federation.