This Thesis presents an analysis of the Brazilian Juvenile Justice System, focusing on the paths taken by teenagers in the investigation phase of the act considered infraction. The research was built with a qualitative approach and was based on historical-dialectical materialism, based on critical criminology studies. The following research sources were used: participant observation; analysis of technical reports on the socio-educational precautionary units, prepared by the technical team of Social Service of the Public Ministry of RJ and interview with a professional from the Socio-educational System of DEGASE. The general objective of the research is to analyze the Juvenile Justice System, to understand how the functioning, conditions of services, routines, flows, decisions, and other actions are operated by the Juvenile Justice System bodies, in the light of the normative instruments in force. The results showed how the State, even with the advance of normative instruments to protect children and youth, criminalizes the poorest adolescents and imposes a racialized punitive selectivity to absorb them in the Juvenile Justice System. Once inserted into the gears of the system, it was possible to verify the dimension of institutional violence that crosses all paths from apprehension, provisional internment, until the holding of hearings - a period in which they are still under the constitutional guarantee of presumption of innocence. In these cases, there is an early punishment of an infraction not yet judged, which is naturalized in the daily life of the bodies that make up this system and materializes in a scenario of violation of individual and collective rights, which reinforces the process of dehumanization and the trivialization of their lives.