In the present legal situation, the issues of so-called difficult evidence undoubtedly deserve a serious discussion not only on its preservation and storage but also with regard to an investigation process in terms of the efficiency of relevant services dealing with counteracting possible threats to the state. This neglected by the Polish legislator issue is also of tremendous importance in view of an organizational and legal system for fighting crime. Therefore, the Police Academy in Szczytno carries out scientific research, financed by the national Centre for Development and Research, as part of a development project on ‘Infrastructure, equipment and
technical and legal procedures concerning the preservation and storage of difficult evidence’, which aims at the creation of infrastructure, equipment and technical and legal procedures in relation to the preservation, storage and utilization of difficult evidence. The article presents the diversity and unique nature of difficult evidence-related procedures for identifying the most effective methods of preventing crime as far as the national security is concerned.