This chapter captures the role of the prosecutor or an equivalent authority during the trial phase. The object of the analysis—the trial phase—is generally divided into the following stages: opening stage, presentation of evidence, closing stage, and judgment/sentence. In exceptional cases, the stage of jury selection is added. The perspective of the analysis is twofold: in the first half of the chapter, the prosecutor’s role at these stages is described from a normative perspective. Here, the stages mentioned are broken down into selected prosecutorial measures and procedural facets in various legal systems and procedural models. The legal systems and procedural models analyzed have been chosen to represent either the common law tradition (the United States, England, and Wales) or civil law tradition (Germany and France). In the second part of the chapter, the prosecutor’s role is analyzed from an ethical perspective. It displays both the features and normative foundations of prosecutorial ethics and describes certain types of prosecutorial misconduct that may occur in the previously mentioned stages of a trial. The findings and observations of the chapter are combined in a conclusion at the end of the chapter. Upon identifying the multiple roles of the prosecutor at trial, the chapter proves that prosecutorial work at trial is influenced by two role-related factors: role duality and role ambiguity.