Effective investigation of war crimes is impossible without the proper use of specialized knowledge. The peculiarity of proving in such criminal proceedings lies in the combination of traditional forensic approaches with new challenges posed by martial law, the digitalization of information, and the need for prompt recording of the consequences of armed aggression. That is why the article’s purpose is to examine the features of expert conclusions in proving war crimes and to assess their place in the system of evidence sources. The study found that, despite legislative consolidation of the possibility of a specialist drawing up reports and conclusions, this form of implementing specialized knowledge has not yet become widespread in law enforcement practice. Instead, the traditional model of involving a specialist as a participant in investigative (detective) actions remains dominant, with the results formalized as certificates, explanations, and technical annexes to the protocols. It is determined that this form of using special knowledge ensures their procedural admissibility and integration into the evidentiary system without violating the requirements of criminal procedural legislation. It is substantiated that a promising direction of development is to expand the possibilities of using the results of special research in the form of expert conclusions in evidence, however, subject to clear regulatory regulation of the procedure for their preparation and evaluation. The need to distinguish the competence of an expert and a specialist, to prevent the substitution of their procedural functions, and to improve the provisions of criminal procedural legislation, in particular in the context of the application of parts 8 and 9 of article 71 of the Criminal Procedure Code of Ukraine, is emphasized.