In this article separate aspects of interrogation tactics for suspects (defendants) suffering from mental disorders are reviewed. The currency of the subject is based upon the statistics, according to which the increase of the number of such participants in the preliminary investigation is observed. The publication includes the preparation for interrogation and the interrogation of the suspect (defendant) whose psychic setup is recognized as inadequate to the situation of the investigation process. It is recommended to examine the psychic setup of the person under interrogation in the course of preparation for the interrogation should the investigator have reasons for it. A psychiatrist may render assistance in receiving such information by examining the suspect (defendant) before interrogation. In the course of interrogation it is recommended to use basic tactical methods as well as special ones caused by the revealed mental disorder of the suspect (defendant). The involvement of the psychiarist who can control the psychic setup of the suspect (defendant) into interrogation for the purpose of rendering assistance to the investigator may serve as a special tactical method