The article presents the results of the analysis of some provisions of regulatory legal documents establishing the procedure for determining the severity of harm caused to human health. Attention is drawn to the fact that the essence of normative legal acts presupposes a strictly fixed meaning of the terms used in them, the unambiguity of the guidelines, compliance with the laws for the implementation of which they are adopted, and internal consistency. The analysis of the Rules and Medical Criteria for determining the severity of harm caused to human health shows their non-compliance (to a greater or lesser extent) with the specified requirements, which actualizes the need to make appropriate changes and additions to these documents.

Background: The European criminal law system declares principles of competition and equality of parties as fundamental to ensure respect for human rights and fundamental freedoms. The domestic legal system also contains these concepts, but only the principle of competition, which includes equality, is declared as a fundamental principle. Such a seemingly insignificant difference in systems causes difficulties in implementing these principles in criminal proceedings, which is shown by the example of using special knowledge in the form of expert opinion and interrogation, and those few tools for the defense that can be used for qualified opposition by the prosecution, which builds its system of evidence on the experts conclusion. Vividly, implementation contradictions in the criminal process principles of equality and competition occur with the use of one of the parties (mostly by the defense) specialized knowledge in the form of imprisonment and interrogation specialist. Aims: This study aimed to analyze the problematic issues that arise in this case. Conclusion: Results of the study show the need for practical development and greater legal significance to the institution of participation of a specialist in criminal proceedings, both directly and separately through a written opinion, which meets not only the principles of modern improvement of the implementation of constitutional guarantees for justice, court access, and obtaining professional legal assistance, but also the provisions on the right to a fair trial, provided for in art. Six conventions for the protection of human rights and fundamental freedoms ETS N 005 (Rome, 4 November 1950) are ratified by the Russian Federation on March 30, 1998.

The article reviews the contradictions between the procedural law and an attorney’s professional duty to use an opinion of a knowledgeable person in the system of criminal procedure protection. The paper provides an analysis of the problems and difficulties arising in the implementation of this right in the criminal process leading to violation of the equality and adversarial principles: the optionality of the defense’s right to involve a specialist; the biased attitude of law enforcement agencies to the expert presented by the defense; the desire to diminish the probative value of the specialist’s conclusion and testimony; the absence of an obligation for an investigator and court in all cases to attach the expert’s opinion to the case. The author emphasizes how important it is for all the participants in the criminal process to understand the expert’s opinion and testimony’s independent evidentiary value. Proposals that contribute to the legal specificity and further development of the specialist institution within the framework of the fundamental principles of competition and equality of the parties are presented.