The article examines the importance of involving a specialist in criminal proceedings as a person who, unlike the subject of the investigation, has such professional competences (in the form of knowledge and skills) that allow establishing factual data about the circumstances relevant to the proceedings. Cases of mandatory involvement of a specialist in procedural actions are determined.
 Attention is focused on the correct definition of the purpose of involving a specialist in procedural actions - gathering evidence, in connection with which the opinion is substantiated regarding the importance of such registration of the results of the involvement of a specialist, which would ensure the appropriateness and admissibility of the collected evidence and their further use in the proving process.
 An analysis of the types of fixation of the involvement of a specialist in criminal proceedings determined by the Criminal Procedure Code of Ukraine is carried out and an assessment of their procedural capacity is carried out in relation to the defined purpose of the involvement of a specialist. Conclusions about the inability of certain types of fixation of the specialist's involvement in procedural actions defined by the legislator as evidence are substantiated. Emphasis is placed on the loss of evidence when choosing such types of fixation of the involvement of a specialist.
 The advantages of this type of fixation of the results of the involvement of a specialist in criminal proceedings are determined as a written explanation of the specialist who participated in the relevant procedural action, attached to the proceedings as an appendix to the protocol. By analyzing the constructions of criminal procedural norms, the place of such explanations in the system of procedural sources of evidence is determined. The position regarding the possibility and expediency of forming written explanations of specialists in the form of certain professional conclusions is substantiated.
 The opinion is advocated regarding the need to replace a specialist's written explanation, as a form of reflecting the results of his application of his professional competences, of such a "dead" institution in the investigation of criminal misdemeanors as a specialist's conclusion, which did not find its implementation in the practical activity of pre-trial investigation bodies.
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