This thesis aims to analyze the trajectory of Elysio de Carvalho during his years at the Identification and Statistics Office of the Rio de Janeiro Police Department, between 1907 and 1915. Elysio de Carvalho built alliances and promoted transnational exchanges in the emerging field of scientific police, by translations, edition of specialized magazines and books, organization of police conferences, and the creation of a police school. His position as a translator and interpreter of this new space of expertise - produced at the interface between police and science - is studied here through two research strategies. First, localizing his trajectory in the police within a longer itinerary, marked by the displacement from Alagoas to Rio de Janeiro and successive attempts to become a recognized writer in the Capital City. Second, exploring the conflicts in the Identification Office s everyday life, its relationship to other sections of the police, and the political disputes of the Brazilian First Republic. From his police office, Elysio de Carvalho has sought to dialogue with the international networks of police cooperation, in order to build a local career as a civil servant. Taking distance from the interpretations that saw in this years as the chief of the Identification Office a radical break with its previous trajectory, by considering the condition of writer and police officer as irreconcilable, this thesis proposes to explore the field of possibilities of a writer within the Rio de Janeiro police in the beginning of the 20th Century.