The present work gathers the results obtained through a case study about the performance of the Central de Inquéritos de São Luís - MA. It is a qualitative-quantitative research, of an evaluative type, based on the use of the inductive method. For this purpose, the analysis procedures of 109 judicial decisions issued by the agency between June and July 2019 were used as research procedures, as well as the compilation and organization of official data on provisional incarceration at the municipal and state level. Its main objective is to re-discuss the official legal foundations that affect the application of provisional detention at the local level. To comply with this directive, the analysis focused on unveiling the arguments used by the judges to justify the decree of provisional deprivation of liberty. It was concluded that, differently from what is passed through the official legal-criminal discourse, provisional arrests, in most of the situations verified, are not used as a precautionary measure, but as a true anticipation of the deprivation of liberty.