The article analyses the "defensive dominant" concept. Based on the works of the renowned Russian physiologist A.A. Ukhtomsky, the author proposes a definition of the defensive dominant and presents examples from judicial practice that demonstrate the mechanism of its operation. The study reviews psychological defense mechanisms employed by suspects (the accused) held in custody, as well as by individuals convicted of extremist and terrorist crimes. A conclusion is drawn on the necessity of analyzing brain MRI and CT scan results to gain insight into the neurobiological nature of the defensive dominant, with the aim of enhancing the effectiveness of communicative investigative actions.