German administrative law is characterized by the idea that the authorities and, in the case of a lawsuit, the administrative judges have sovereignty over the investigation of the facts ‐ the so-called principle of ex officio inquiry (Section 1). In the relationship between the official and judicial investigation of the facts, it is striking that the judicial duty to investigate is not limited by the official duty to clarify the facts. This shift in the direction of a judicial right of final decision, also with regard to the factual basis of administrative decisions, derived from the German Constitution (Article 19(4) Grundgesetz) can probably only be explained by the historical background of National Socialist despotism. The article reveals that the instruments of evidence collection (Section 2), the consideration of evidence (Section 3), the evidential standard (Section 4) and the burden of proof (Section 5) are based on the principle of ex officio inquiry. This principle is based on the assumption that only a perceivable set of facts can be established. Therefore, practice and sectoral administrative laws show that in areas where obtaining knowledge is particularly difficult, the principle of ex officio investigation and the law of evidence based on it must be modified and, in particular, strong participation of the parties in obtaining the facts must be made possible. At the same time, the German law of evidence is based on theories and instruments of civil procedural law, which is characterized by the principle of production of evidence. Against this background, the article aims to illustrate that, contrary to the first impression, German administrative law does not implement the principle of official investigation in its pure form, but it is understood in a refined open and area-specific manner.
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