Principle of unity of the language of the proceedings
Although the reasons for the decision under R 111(2) EPC need not deal with all the arguments of the parties in detail, they must at least deal with the decisive points of dispute. They shall deal with the relevant facts, evidence and arguments and contain the logical chain of reasoning which led to the conclusion drawn. The principle of unity of the language of proceedings applies to proceedings before the EPO. Only the language of the proceedings shall be used for the written decision. Only a decision in a uniform language of proceedings also meets the requirements of Rule 111(2) EPC for the grounds of the decision. According to Art 125 EPC, insofar as the EPC does not contain any provisions on procedure, the principles of procedural law generally recognized in the contracting states of the European Patent Organization shall be applied. This applies in particular to the general legal principle of a fair trial, which is also expressed in an exemplary manner in Art 6(1) ECHR and serves as a general guideline for the organization of proceedings. This also includes the requirement to draft the decision in such a way that it can be understood by a party who speaks the language of the proceedings (EPO BoA 12 April 2021, T 1787/16, Verfahrenssprache).