Forensic psychiatry, as a specific branch of psychiatry, is the medical science that approaches mental illness and its relation with law enforcement. In this regard, medicine and justice converge in the contact with individuals that, due to the alleged assumption of acting under the effects of a psychiatric disease, have a disturbing behaviour and infringe the laws of Society. The objective of this research project, which has a retrospective nature, is to delineate the profile of the mentally incompetent patients of the Local Health Unit of Guarda, Portugal, resorting to the reports of mental faculty's examinations of, at least, 30 individuals. With this methodology, we will be able to study the characteristics of selected individuals who have committed some sort of criminal offences but are not subject to prosecution, namely with regard to the specific personal and family data, psychiatric background, diagnostic formulations, applied legal concepts, among others. Statistical analysis was carried out using the Microsoft Excel tool. The main goal of the study is to provide to the Psychiatry Department of the Local Health Unit of Guarda an analytical instrument that characterizes the respective mentally incompetent population and may, essentially, contribute positively to the contextualization and accomplishment of the future assessments on mental faculties of the individuals who are involved in judicial proceedings.