The decisions reported below concern requests that the board take evidence from an independent expert under Art. 117(1)(e) EPC and R. 121 EPC (the case law shows that the boards refused those requests). Such cases are to be distinguished from those where opinions of a party's expert are submitted as evidence (which are more common) and in which the department in question will evaluate the opinion's probative value; see in this chapter e.g. T 1676/08; T 658/04; T 885/02; T 276/07 (language); T 74/00 (legal expert opinion, Japanese law); T 517/14 (right of priority, legal expert opinion, Israeli law); T 1201/14 (transfer of right of priority – legal opinion from legal expert on US law regarding nunc pro tunc assignment and from professor regarding Taiwanese law, but in this case the evidence adduced could not prove that the appellant was the owner of the right of priority, irrespective of the formal requirements of any relevant national law (US, German or Taiwanese) alleged); R 18/09 (late-filed external legal opinion on the admissibility of the petition); T 156/15 (opinion of a former board member submitted as expert evidence, addressing issues which had been part of the appeal proceedings from the start and filed two weeks before the oral proceedings); T 2132/16 (new evidence filed at a late stage – not admitted – containing the opinion of different technical experts and a transcript of their cross examination in a UK court case; documents including no new technical facts; board in a position to decide without the further technical assistance provided by these experts).

An opinion of a party's expert is a means of evidence under Art. 117(1) EPC (T 517/14, point 2.8.4 of the Reasons). T 753/09 stated that an expert declaration had to be regarded not just as an argument, but as evidence pursuant to Art. 117(1)(e) EPC.

In T 375/00 the board, ruling on the opponent's request that it order an expert opinion under Art. 117(1)(e) EPC, held that actively seeking experts to help the case of one of the parties could leave it open to an accusation of partiality and that it was for the parties to find the evidence they needed. Only if the board did not consider itself in a position to decide upon a matter without technical assistance would expert evidence within the meaning of Art. 117(1)(e) EPC become appropriate (T 1676/08, citing also T 395/91, point 5.3 of the Reasons, T 230/92, point 5.3 of the Reasons, T 375/00, point 1.2.2 of the Reasons, and T 311/01, point 5 of the Reasons). Other cases rejecting a request for an expert opinion: T 1548/08, T 1763/06.

In T 443/93 too, the board refused a request for such an expert opinion made at the oral proceedings after a witness had been heard, noting that the appellant had neither filed the request on time, nor supplied specific grounds justifying such a request at that stage in the proceedings.

In T 392/06, during oral proceedings the respondent (opponent) requested the appointment of an independent technical expert in view of the contradictory experimental results of the appellant (proprietor) and the respondents (opponents). The board had no reason to substitute for the respondents to compensate for their deficiency in the provision of the evidence which supported their objection of lack of novelty in allowing an independent expert. Furthermore, commissioning of an independent expert would have made postponement of the oral proceedings necessary, which was contrary to Art. 13(3) RPBA 2007 (see also the obiter dictum in T 998/04, reported in this chapter III.G.5.1.1, on the burden of proof).

T 8/13 addressed several procedural aspects. On the request formulated by the appellant (opponent) to hear an independent expert of a university, the board considered that the questions on which it had to decide did not require any further technical expertise to be gathered from outside the Office. The appellant did not provide any further argument as to why hearing an independent technical expert would have been required in order to decide on this case. There were thus no good reasons why the board should have exercised its discretionary power under R. 117 EPC as requested by the appellant.