§1. If the ordinary has decreed that a judicial penal process must be initiated, he is to hand over the acts of the investigation to the promoter of justice who is to present a libellus of accusation to the judge according to the norm of cann. 1502 and 1504.
§2. The promoter of justice appointed to the higher tribunal acts as the petitioner before that tribunal.
Source: Code of Canon Law (Vatican.va)