Numerous international and domestic studies have shown that all the duties which law enforcement personnel perform put an increased strain of mental and physical health. All this makes the aptitude testing system of the professionals essential and at the same time more important. An essential condition for the effectiveness of such a system is to be able to continuously adapt to changes in organizational needs and the characteristics of applicants for the organization. The explosive growth in digitalization and the use of the World Wide Web has posed a revision of the more than ten years applied aptitude test system for law enforcement professionals as law enforcement challenges and the younger generation’s changed abilities and motivation to work. In response to these challenges, the Two-stage Integrated Aptitude Testing System (abbreviated as KLIR) was established by Decree No. 45/2020 on the suitability assessment of professional staff and law enforcement administrative staff employed by certain law enforcement agencies under the Minister of the Interior. (XII.16.) BM. Regulation entered into force on 1 January 2021. In our study, we describe the scientific basis of the KLIR system, discussing it along the most important principles of the system. We show how the two steps of the KLIR procedure –examining the fit of work of individuals on several levels at the same time – serving the selection of the most suitable candidates and in addition to the screening of unsuitable ones, thereby improving individual and organizational performance. In the spirit of flexible adaptability, which is considered to be one of the keys to organizational efficiency, we describe the possibilities of the innovations of the KLIR procedure, the scheme of aptitude test categories, the three-level regulatory order, and the coherency between aptitude tests and the training system. The article concludes with a description how the targeted scientific research has contributed to the development of the KLIR system and provides a glimpse of relevant future perspectives.