``The undercover agent: investigation’s instrument and evidence in the fight against organized crime´´

In this thesis we analyse one of the most efficient instruments or tools for combating organised crime: the undercover agent. This figure is described and delimited from its two main profiles in the criminal process: as an instrument of investigation or criminal investigation diligence in the investigation and as a means of evidence in the oral or plenary proceedings. In the study of the first of their profiles, we explain what their characteristics are, that they must be authorised, who can carry out this activity, that they are given a false identity and that they have a plan for the undercover operation, and that they must transmit the information they gather to investigative court. We delimit their scope of action, which is organised crime, and within this we specify that they can only investigate the crimes listed in art. 282 BIS of the LECrim. Subsequently, we focus on the measures and resources to protect the undercover agent during the process and establish the limits of their action as an investigation's instrument. In the study of the second of its profiles, we explain that the minutes provided by undercover agents as well as their testimonies constitute evidence and we try to define what type of evidence we are dealing with. We also analyse the evaluation of this evidence and the evidential weight given to it by doctrine and jurisprudence. We also establish the limits of the undercover agent's testimonial evidence. Subsequently, we systematise the criminal, disciplinary and civil responsibility that could be incurred. Finally, we analyse the virtual undercover agent. We describe and criticise the current regulation of the international action of undercover agents and, we focus on examining the regulation given to them by the Italian legal system. Concluding with some lege ferenda proposals accompanied by the most important ideas.