Art. 117 EPC indicates the types of evidence permitted "in proceedings before the European Patent Office" thereby providing for the submission of evidence before all EPO departments, including the Receiving Section, examining divisions, opposition divisions, the Legal Division and the boards of appeal.
The EPO departments must ascertain the relevance of evidence submitted to them before deciding whether to admit or reject it - only in exceptional circumstances need they not do so (T 142/97, OJ 2000, 358). In this respect, R. 116 EPC (former R. 71a EPC 1973) should not be construed as an invitation to file new evidence or other material departing from the legal and factual framework of issues and grounds pleaded and evidenced throughout the proceedings prior to the hearing of the appeal (T 39/93, OJ 1997, 134).
According to T 716/06, it is true that where oral evidence of a witness is requested by a party the competent EPO department should grant this request only if it considers this oral evidence necessary, i.e. when it is required to clarify matters that are decisive for the decision to be taken. If a request is made by an opponent to hear a witness on an alleged public prior use and on the disclosure of a certain feature by this prior use, the competent department of the EPO must as a rule grant this request before deciding that the alleged public prior use is neither established nor a novelty-destroying part of the state of the art because the feature in question is not found to be disclosed therein.