"Psychopathy" describes a type of personality disorder characterized by a dysregulation of emotion processing. Social behaviour, emotion regulation and competency are of particular relevance in forensic psychiatry. Structural-morphological and functional imaging studies prove that emotion regulation, aggressive-impulsive behaviour and learning from negative experiences are greatly influenced by frontal brain regions. These abilities are impaired in severe cases of dissocial personality disorders and in traumatic "pseudopsychopathy". We illustrate the importance functional neurobiological changes in patients personality disorders and "acquired psychopathy" by two case reports on patients who were admitted to a forensic-psychiatric facility for sexual crimes.