Courts have showed to be key political actors and, at times, important promoters of social change. However, not enough attention has been devoted to the role of lower courts as effective enforcers of the rule of law, especially in relation to crimes involving state agents. Similarly, while scholars have examined in-depth the nature and causes of corruption, few, if any, studies focus on its effective judicial prosecution. Therefore, this dissertation aims at answering the following question: under what conditions can lower courts effectively hold corrupt politicians accountable? I examine this question in relation to the Italian judicial and political scenario. Italian politics has long been marred with corruption, until a judicial breakthrough occurred in 1992, with the so called "Clean Hands investigation." This dissertation examines the conditions that promoted the effective judicial prosecution of systemic corruption in the Clean Hands investigation, and its diffusion across Italian jurisdictions. I argue that judicial effectiveness depends on the structure of professional relationships among judicial actors, both at the national and local level. First of all, I argue that the overall flattening of the judiciary branch creates the conditions for the emergence and diffusion of legal innovations among its lower ranks. Secondly, jurisdictions where the relationship between local judicial authorities and their subordinates is hirarchical will impede the effective prosecution of complex criminal issues. In contrast, jurisdictions where the relationship between local authorities and lower ranked judges has been "flattened" will be more prone to the emergence and diffusion of legal innovations, and, as a result, to the aggressive and effective prosecution of complex criminal issues, including systemic corruption.I test this theory through a longitudinal analysis of the Italian judiciary's transformations over the years, and through the case studies of four jurisdictions: Milan, Rome, Palermo and Reggio Calabria. Case studies are paired to control for potential confounding variables that might affect the judicial prosecution of complex criminal issues in each of these judicial units. The use of process tracing allows me to detail the significance of local judicial relationships for the judicial prosecution of systemic corruption in each of these case studies.