In this article, the author examines the systemic problems of protecting the rights of victims in the investigation and consideration of criminal cases. The passive role of the victim in the criminal process is revealed. The lack of activity of the victim is explained by historical factors and the general low legal culture of the population. Conclusions are drawn about the discrepancy between the status of a party to the criminal process and its rights granted to the victim, and the actual possibilities for the victim’s participation in evidence. The features of the victim’s participation in the proof are investigated. The specificity of the proof process with the use of special knowledge is established, as well as the specificity of the use of special knowledge by the victim in proving. The significance of special knowledge for effective protection of the rights and legitimate interests of the victim is revealed. The significance of the expert’s conclusion and testimony as evidence for the protection of the rights and interests of the victim is established. The author defines the expert’s opinion as evidence that allows the victim to use the rights granted to him to protect his interests in the process, which do not always coincide with the interests of persons conducting criminal proceedings. The author reveals the problems of using the conclusion and testimony of a specialist as evidence. The article formulates theses on the need to improve the law on the use of expert opinion and testimony in criminal proceedings, on the need to balance the interests of the victim and the accused in the use of special knowledge in the investigation and consideration of criminal cases.