To them above all the public prosecutor's offices and the police ( in Germany the police of the countries, the federal police and the Federal Criminal Investigation Office ) belong, in addition, the customs administration as well as in the range of the delivery right the financial administration with their fiscal investigation.
The police is usually that prosecution authority, which attains knowledge as the first of the suspicion of a criminal offence, z. B. by a charge. She has to investigate then in the context of a preliminary investigation circumstances. Even if in practice the police up to certain procedure conditions determines independently, this Verfahrensabschnitt is led legally by the public prosecutor's office, which is instruction-authorized in relation to the police. One speaks to that extent of the public prosecutor's office as „a lady of the preliminary investigation “.
The prosecution authorities use the law of criminal procedure, in Germany thus primarily the code of criminal procedure. They are bound to the legality principle, i.e. must be followed fundamental to each suspicion of a criminal offence officially, without a discretion of the authority would exist to that extent. Of it there are however exceptions after the Opportunitätsprinzip.