2.4.4 Expert opinion submitted by a party

Following on from the section on expert opinions ordered by a board (Art. 117(1)(e) EPC), this section relates to expert opinions the parties themselves furnish as evidence (as occurs most often in practice).

In G 1/22 (OJ 2024, A50) the Enlarged Board noted in point 66 of the Reasons that parties are regularly requested to file evidence (such as a legal opinion from an independent law expert) concerning the effects of the applicable national law.

In T 517/14 (priority right, Israeli law) with regard to an expert opinion submitted by the appellant the board noted that, while an opinion by an expert who has represented a party "in numerous proceedings" may, upon free evaluation of the evidence, have carried less weight than a court decision, another independent authority under the national law or an expert commissioned by the board under Art. 117(1)(e) EPC together with R. 117, first sentence, EPC, an opinion of a party's expert was a means of evidence under Art. 117(1) EPC.

In T 1117/16 the appellant had presented two pieces of written evidence, which it referred to as "affidavits". In the board's view, since the list in Art. 117(1) EPC was not exhaustive, there was no cause to decide whether the submitted pieces of written evidence were indeed affidavits. The issue of what type of statement this evidence was may, at best, be important for the probative value of those statements. However, the board held that Mr D's "expert opinion" was not an opinion by an expert as per Art. 117(1)(e) EPC but a "party opinion" that was to be regarded as nothing more than a written statement by a third party not involved in the proceedings. The available documents were prima facie unsuitable for proving up to the hilt that the subject of prior use oV3 had been sold and delivered as alleged. Ultimately, oV3 was not admitted into the proceedings (Art. 13(1) RPBA).

In the following cases, the boards likewise dealt with expert opinions offered by a party: T 1676/08, T 658/04, T 885/02, T 276/07 (expert opinion not translated from Italian), T 74/00 (legal expert opinion, Japanese law), R 18/09 (external legal opinion on the admissibility of the petition), T 156/15 (opinion of a former board member submitted as expert evidence), T 2132/16 (opinion of different technical experts and a transcript of their cross-examination in a UK court case).

In T 765/21, by submission shortly (two weeks) before the oral proceedings, the proprietor indicated that Mr X, an employee of the proprietor, would attend the oral proceedings and requested that he be allowed to make oral contributions as a technical expert at the hearing. In view also of the fact that no request had been made to summon Mr X under Art. 117(1)(e) EPC and R. 118 EPC, the board concluded that Mr X should be considered as an accompanying person within the meaning of decision G 4/95. As indicated in G 4/95, oral submissions by persons accompanying professional representatives but not covered by Art. 117 EPC cannot be made as a matter of right, but only at the discretion of the board. Without any indication of his qualification or the nature of his intended contribution, the request did not meet the criteria in G 4/95. Furthermore, the opponent did not agree.

See also T 335/15, in which two months before the oral proceedings the opponent had filed a request that a technical expert be heard but did not specify on what point that expert would be speaking until the oral proceedings. The board ruled on the issue with reference to the findings in G 4/95 on oral submissions by an accompanying person. More generally, this issue is discussed in chapter III.V "Representation".