The article deals with local issues of assessing an expert’s opinion: the legality of the subject of initiating a forensic examination and the direct subject of its production. The scope of the Author’s interests, teaching experience and scientific activity make it possible to classify these issues as “latent”, since their non-obviousness is determined both by the established law judicial practice and by the imperfection of the legal regulation of forensic examination in criminal proceedings. Along with the main issues, attention is paid to the genesis of the institution of forensic examination in criminal proceedings, which aims to demonstrate the continuity of its legal regulation, and also to draw attention to the fact that some approaches used by the legislator in the Code of Criminal Procedure of the RSFSR could be preserved in the current criminal procedure law, which would not only prevent the occurrence of a number of issues with the law enforcement officer, but would also serve as an optimization of the production of comprehensive examinations. Evaluation of an expert opinion is a multifaceted intellectual activity that involves the resolution of a complex of procedural and substantive issues. The objects of assessment, along with the expert's opinion, are also procedural documents, which reflect all the actions, the production of which ensured the preparation and appointment of the examination. The list of criteria that the expert opinion must satisfy is standard for all evidence – admissibility, relevance and reliability (part 1 of article 88 of the Criminal Procedure Code of the Russian Federation), but at the same time, the assessment of each of the properties of the evidence “expert’s opinion” should be carried out taking into account the specifics of its formations. At the same time, when evaluating the admissibility of the expert’s opinion, it is necessary to pay attention to data indicating the legality / illegality of the subject of initiating a forensic examination and the direct subject of its production. The Author insists on the need for the subject of the assessment to know the content of the expert's opinion of the entire required set of normative sources and emphasizes that there should be constant monitoring of changes to existing regulations, as well as the publication of new ones related to the area under consideration.

The paper analyzes the errors committed by law enforcement officers in the implementation of various types of special knowledge at all stages of criminal proceedings. Shortcomings under consideration are differentiated into shortcomings committed in the production of investigative actions, during which objects were seized, subsequently presented for an expert examination, when forensic examinations are appointed, in the production of forensic examinations, when examining the expert's opinion by officials of the preliminary investigation bodies and the prosecutor's office. At the same time, such errors are periodically repeated and multiply: forensic examinations, the need for the production of which is caused by the specifics of the crime being investigated, the current investigative situation and, being justified by specially developed recommendations, are not scheduled; the questions posed to the experts do not cover all the circumstances the establishment of which is possible only through the involvement of persons knowledgeable in a particular area of special knowledge; the questions themselves are not always directly related to the expert's specialization and the type of examination; the presence of proper qualifications of a person involved as an expert is not verified, etc.Without setting themselves the task of analyzing all or most of these errors, the authors thoroughly consider the most serious errors using specific examples from judicial investigative practice and they come to the conclusion that the effectiveness and efficiency of using the expert's conclusion in proving is possible only under the context of impeccable observance by officials of preliminary investigation bodies, forensic experts and heads of forensic institutions of the provisions of the Criminal Procedure Law, the Federal Law "On State Forensic Expert Activity", departmental regulations and forensic recommendations.