Before an administrative authority or a court takes a decision, it is required to establish the existence of the material facts, i.e. the facts from which, under the relevant legal provision, the legal effect ensues. The facts are established by taking evidence. The purpose of all evidence, whatever its nature, is to confirm a party's assertions. In view of its purpose, evidence should be distinguished from the term "substantiation" which does not cover evidence, although there may be some overlap when written documentation is furnished as a means of proof (T 543/95). Evidence within the meaning of Art. 117 EPC equals all the legal means other than mere argument that tend to prove or to disprove a fact at issue before the competent EPO department (T 642/92).
The EPC contains provisions governing the means of giving or obtaining evidence, the procedure for taking evidence as well as the conservation of evidence (Art. 117, R. 117 - 124 EPC). Under the EPC Revision 2000, the content of Art. 117(2) to (6) EPC 1973 was rephrased in the new Art. 117(2) EPC. The procedural aspects concerning the taking of evidence were transferred to the Implementing Regulations (see R. 118 - 120 EPC). Furthermore, the revised Art. 117(1) EPC no longer lists the EPO departments which may take evidence, i.e., Receiving Section, examining and opposition divisions, boards of appeal and Enlarged Board of Appeal; it now includes a general reference "proceedings before the European Patent Office".
Beyond the letter of the EPC, the boards of appeal have addressed multiple issues of admissibility and taking of evidence in their case law. In addition, they have elaborated specific principles governing the evaluation of evidence and the allocation of the burden of proof in order to ensure that EPO proceedings are conducted in a fair and consistent manner.