Prosecutors play a decisive role in contemporary criminal justice. Their decisions greatly influence the output of the system, as well as the behaviour of other criminal justice institutions. By harnessing the power to filter, select and segment the work of criminal justice, prosecutors provide structure to an otherwise unbalanced field. They thus play a key structuring role. However, the prosecutors’ position and the problems that emanate from it have mostly been studied in terms of their power and discretion. We contend that this approach neglects the core problems and challenges connected to the prosecutorial function in contemporary criminal justice and offer a reconstruction of the formal and informal influences that shape the behaviour of prosecutors in providing for structure.