The purpose of the article was to consider the main development trends in certain elements of the criminal justice system, which were integrated due to Russia's large-scale attack on the sovereign territories of Ukraine. The subject of the article is the institution of the reform of the Ukrainian criminal justice system. The legal bases ensuring the functioning of criminal justice institutions (in particular, the investigative bodies) are examined and the corresponding conceptual and categorical apparatus is analyzed. A review of selected elements of the criminal justice system during the war is conducted. The influence and significance of Ukraine's acquisition of EU candidate membership status on the functioning of certain elements of the criminal justice system is clarified. Finally, the content and essence of the main requirements of the EU to Ukraine, which can be the basis for conducting negotiations on the issue of Ukraine's final accession to the organization, are characterized. In the conclusions, directions and methods of reforming certain elements of the criminal justice system in the conditions of large-scale invasion are described.