Art. 117 EPC entitled "Means and taking of evidence" is applicable before all EPO departments, including the Receiving Section, examining divisions, opposition divisions, the Legal Division and the boards of appeal. The decision whether to order any of the means of taking evidence listed there depends on whether or not the evidence in question can be considered relevant (i.e. necessary or useful for settlement of the dispute). The decisions reported here deal, essentially, with requests that a witness be heard and it may also be useful to refer to the section in this chapter III.G.2.2., which concerns (refused) requests that an expert's opinion be obtained (Art. 117(1)(e) EPC). Reference is also made to chapter III.G.3.2., which deals with situations when the giving or taking of evidence can be requested or should be ordered. See also in this chapter III.G.3.3., which deals with whether a failure to order that evidence be taken results in an infringement of the right to be heard.

The EPO departments must ascertain the relevance of evidence submitted to them before deciding whether to admit or reject it. EPO departments do indeed have some discretion in admitting evidence offered, for example where it is no longer needed because the fact at issue is not contested by the other party, where the decision will in any case go in favour of the party offering it, where it is submitted very late in the proceedings and is considered immaterial, or where for some other reason it cannot affect the outcome (e.g. evidence offered in an inadmissibly late-filed opposition) (T 142/97, OJ 2000, 358).

In T 798/93 (OJ 1997, 363) the board observed that all the means of giving or taking evidence covered by Art. 117 EPC are subject to the discretion of the department concerned, which will order their use only if it considers this necessary. It then refused the appellant's request for the taking of evidence as to the opponent's identity because it was couched in general terms and did not refer to any specific means. The only specific means requested was a sworn statement in writing but, in the absence of any legitimate doubt as to the opponent's identity, the board considered that this was neither useful nor necessary.

All appropriate offers of evidence made by the parties should be taken up. As a rule, it cannot be considered to be in keeping with good procedural practice for an opposition division not to take up an opportunity to hear a witness or party in evidence (T 329/02; see T 860/01 on the extent of the discretionary power of the first-instance department).

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. In T 2003/08 of 31 October 2012 date: 2012-10-31 the board – in contrast to the opposition division – considered it appropriate to hear the witnesses because their testimony could affect the outcome of the proceedings.

In T 1100/07 (alleged prior use, sale of a vehicle with a given feature), the department of first instance had refused to hear two witnesses. The board held that it had been right to refuse to hear one of them, as he would merely have confirmed what he had said in his written statement about documents that anyway spoke for themselves and hearing him would have had no impact on the final decision. It should, however, have heard the other witness. It was true that the request that he be heard had been filed late and that granting it would have meant adjourning the oral proceedings, but the opposition division had based its final decision on a failure to establish the prior existence of a single given feature and the witness would allegedly have been able to give evidence on that very point. Thus, the refusal to hear him was wrong and might have affected the outcome of the decision. The case was remitted to the opposition division.

In T 361/00 the board explained in detail why, given the circumstances of the case before it, hearing the witness would be unnecessary because it would in no way affect the outcome of its decision.

In T 1231/11 the board refused the request to hear a witness in support of an allegation of prior use. The witness had been offered to confirm the contents of his statutory declaration, but the board concluded that since he had not made any written statement regarding the decisive issue, any information provided on this matter would amount to introducing new facts into the proceedings. In addition the board concluded that there had been no substantial procedural violation by the department of first instance since hearing the witness had not been considered relevant for the outcome of the case. The board found the circumstances to be different from those ruled on in three other cases, where the request to hear witnesses related to facts already on file: T 267/06 (essential details referred to in the affidavit); T 25/08 (hearing necessary in order to confirm what had been brought forward in writing); T 448/07 (need to clarify inconsistencies in a written statement).

In T 1410/14 (prior use – train – test drive) the board remarked in particular that, since the witness whose hearing the opponent had requested would not have been able to testify as to the decisive material facts, such a hearing would serve no purpose.

In T 753/14 the opponent (appellant) requested that the board hear the proprietor of the patent in suit (respondent) under Art. 117(1)(a) EPC to clarify the scope of the disclosure in another of its patents (A10), which the opponent had cited as novelty-destroying prior art. In other words, the proprietor was to be heard with a view to obtaining information that had not been specified in A10 but, in the opponent's eyes, had to be known to the proprietor. The board did not order the requested hearing; it considered it unnecessary as it would provide new information that had not been publicly available on the basis of A10 at the time of filing of the patent in suit (point 1.4.9 of the Reasons).

In case T 30/12, as evidence adduced for proving the invoked public prior use in opposition proceedings, the appellant (opponent) relied upon the drawing A9 and the testimony of Mr H, made before the opposition division. As regards the request for a renewed hearing of the witness Mr H before the board, the board noted that the appellant did not request that the witness be heard again to supplement his testimony by corroborating facts but only to clarify the statements made before the opposition division. However, the statements made by the witness as to whether document A9 was handed over to a member of the public were clear and unambiguous. The request to rehear Mr H was eventually rejected by the board.

In T 544/14 re-hearing the witness was necessary. In view of the complication and the subsequent delay in the proceedings, the board decided first to clarify whether the alleged public prior use was novelty-destroying (without any doubt, no).

Decision T 401/12 of 8 November 2017 date: 2017-11-08, in which the taking of evidence requested by both parties was considered necessary, is an example of an interlocutory decision ordering that evidence be taken by hearing witnesses at a future date (R. 117 EPC) and dealing with the associated costs (R. 122(1) EPC) and the language issue (R. 4(3) EPC). The witnesses were given permission to bring any relevant documents. See also T 738/04 of 22 August 2008 ordering the hearing of a witness under R. 117 EPC at the oral proceedings on 11 December 2008, at the end of which the final decision was taken.