One of the current trends in the procedural law in Ukraine is the functioning of the legal expert institute.The participation in the case of legal expert known as “amicus curiae”, born in the XVII century in Britain is an achievement of the Anglo-Saxon legal system. Its borrowing by the national legal system is the result of convergence, the precedent law system and the Romano-Germanic legal family, a trend that has emerged over the past two decades. The need to involve this person is caused by the same circumstances as the involvement of experts from other fields of science and technology. Namely, the need to obtain special knowledge, which the court due to its professional orientation does not have.The involvement of legal experts may be considered questionable in the light of a judge's professional experience. At the same time, it is not accidental that it is necessary to resolve one or another particular legal case, taking into account the developed theoretical approaches to the application of legal norms that may have certain conflicts with each other in the regulation of disputed legal relations. Therefore, their activities are not aimed at establishing evidence, but are in the nature of a consultative explanation of the mechanism of law enforcement in resolving the case.The result of legal expert's procedural activity is legal expert opinion - new or significantly improved law enforcement decisions obtained during research, which can be introduced into the law enforcement practice of the court in the administration of justice during the proceedings.There is no doubt that the subject of expert activity is limited to a range of issues related to the conflicting use of legal rule.Since justice in Ukraine is administered by a judge who may appoint a citizen of Ukraine who has a higher legal education and professional experience in the field of law, there is no doubt that the vast majority of disputable matters are resolved by him/her independently. At the same time, the inconsistency of the legal system and the legislative system, due to both objective (inconsistency of the level of development of society degree of regulatory regulation of relevant relations) and subjective (incompetence of the legislator, excessive politicization of the rule-making process) factors creates logical and structural defects in the legislation of Ukraine, one of the mechanisms to overcome which is the application of the analogy of law and the analogy of statute. This pro...