In Russian criminal lawthe fact of committing a crime for the first time determines the operation of the fundamental institutions: responsibility and punishment. The identification of the person having committed a crime for the first time is an extremely important task not only for the further proper focus for law enforcement officials on the individualization of punishment and criminal responsibility, but in general, for a more clear perception of the enforcement of the criminal legal relations caused by the criminal act. Despite the importance of this concept, if attention is given thereto in theoretical research, it is mainly from the point of view of clarifying the legal content. The questions of expediency of introducing the concept of a person who has committed a crime for the first time into the text of the criminal law, the criminal legal significance of this circumstance among others affecting the adoption of a criminal legal decision remain little explored to date. Any concept that is applied in practice and has real significance for the qualification of crimes, determining the grounds and limits of criminal liability, as well as for the imposition of punishment, undoubtedly requires criminal law consolidation. The absence of any concept of such significance in the law means that there is a gap in criminal law. Meanwhile, the concept of a person who has committed a crime is complicated by the fact that in real law enforcement it is filled with specific legal content, different from the everyday understanding of this phenomenon. This causes problems such as the association of such persons with "legally non-indictable persons". Full identification of these concepts does not allow the legislator to provide a sufficiently selective, individualized and adequate approach to different categories of such persons. In addition, questions are raised about the differentiation of responsibility of a person who committed a first-time careless crime with a person guilty of committing an intentional criminal act. The paper attempts to answer these questions by the example of specific criminal legal norms, taking into account the experience of their enforcement.