An opposition division's refusal to consider evidence filed in due time infringes a party's fundamental right to free choice of evidence and the right to be heard (T 142/97, OJ 2000, 358).

Pursuant to Art. 113(1) EPC each party must be allowed to comment on any evidence legitimately submitted in the proceedings. Allowing one party, even the party that originally submitted the evidence, to require unilaterally and arbitrarily that the evidence be withdrawn or excluded from consideration would infringe this right (T 95/07; cf. the case in T 760/89, OJ 1994, 797, concerning a return of documents filed as evidence).

As a rule, if assertions made in an unsworn witness declaration ("eidesstattliche Versicherung") remain contested, a request from a party to hear the witness must be granted before these assertions are made the basis of a decision against the contesting party. In T 474/04 (OJ 2006, 129), the opposition division had revoked the patent in suit because the invention did not involve an inventive step over the prior use evidenced in the declaration in lieu of an oath. Since fundamental assertions made in the declaration had been contested, the author was offered as a witness. Although the appellant (patentee) had consistently demanded that the author be heard, the opposition division decided not to summon him as a witness, even though he was available. In the board's view, the appellant had effectively been prevented from making use of a decisive piece of evidence (decision extensively cited in T 190/05).

Failure to consider evidence will normally constitute a substantial procedural violation in that it deprives a party of basic rights enshrined in Art. 117(1) and Art. 113(1) EPC (T 1098/07). In T 135/96 (point 3 of the Reasons), ignoring documents (and arguments) relevant to inventive step was found to violate the party's right to be heard. The board in T 1110/03 (OJ 2005, 302) made a similar finding where indirect evidence substantiating an allegation of fact relevant to novelty was disregarded. In T 1110/03 the board observed that Art. 117(1) EPC and Art. 113(1) EPC embody a basic procedural right generally recognised in the EPC contracting states, viz. the right to give evidence in appropriate form (specifically by producing documents under Art. 117(1)(c) EPC) and the right to have that evidence heard (T 1110/03); except to the extent that they were expressly excluded from the debate (T 2294/12). In T 1536/08 the opposition division had infringed the opponent's right to be heard by completely ignoring the unambiguous offer in its notice of opposition to provide the original printed versions of crucial prior-art documents (see also chapter III.B.2.4.5 "Failure to consider evidence").

In T 838/92 the board observed that in applying the principle of free evaluation of evidence, the opposition division or the board of appeal must exercise caution when evaluating the testimony of a witness whose impartiality is in doubt, with the parties of course being given an opportunity to comment on that testimony (Art. 113(1) EPC 1973). The board was not minded to sustain the appellant's objection to consideration of court bailiffs' reports on the basis that they had been established unilaterally. Such documents recording findings of fact were merely pieces of information which could be added to the file as evidence once they had been submitted to the parties for comment. In T 909/03, where one of the appellants had objected to the manner in which a witness had been heard, the board held that it was not necessary for a party to be given a copy of the minuted testimony before questioning a witness. During the oral proceedings the party had been given sufficient opportunity to comment on the testimony of the witness.

In R 6/12 (case T 928/10) the Enlarged Board considered unfounded the assertion made by the petitioner (opponent) that it had been surprised by the board's failure to order that expert witnesses be heard. The petitioner could and should have taken an active part in the proceedings and, in particular, it was up to it to inform the board during the debate of any need to hear witness to support its line of argument. In its second ground for review, the petitioner contended that the board's decision did not take account of its arguments in general or, more specifically, the submissions of an assistant expert. The Enlarged Board dismissed the petitioner's claim to have been denied its right to be heard as unfounded. The board was not obliged to address in detail each and every argument presented by the party. The Enlarged Board had already found in R 21/09 that, on the pretext of an alleged infringement of the right to be heard, it was actually being asked to review the substance of the decision. This clearly fell outside the ambit of review proceedings, it being solely a matter for the board to decide whether to take a piece of evidence into account and, if so, to determine its probative value.

In T 267/06 an affidavit with an attached, undated drawing (item D12) and a witness hearing had been offered as evidence of the public prior use claimed in the notice of opposition. The opposition division had rejected the opposition to the European patent. The only reference it had made in its decision to the offer of a witness hearing as evidence was in the "Summary of facts and submissions", while the reasons dealt exclusively with the item D12 affidavit and drawing. In the board's view, essential details referred to in the affidavit and deemed to be illustrated in the drawing seemed not to have been taken sufficiently into account by the opposition division. In those circumstances, the witness hearing offered as further evidence should not have been disregarded for the purposes of assessing the claimed public prior use as per D12. This amounted to a fundamental procedural violation (Art. 113(1) EPC). This decision was cited in T 1231/11, but the board there held that the two cases differed.

In T 1363/14 the board pointed out that no EPC provision required that the facts adduced in support of alleged prior use actually be proven within the opposition period in order to substantiate the allegation; rather the requirement was for opponents to submit all the relevant facts and, should the other party dispute them, as a precaution offer suitable evidence. It was in the nature of offering witnesses to state that they would corroborate the facts (already) alleged. It was not permitted to speculate about what a witness would be able to remember and what not, thereby pre-empting the evidence's evaluation. The principle of unfettered consideration of the evidence did not apply until after it had been taken and could not be used to justify not taking evidence offered. Thus the opposition division's refusal to summon the witnesses had arbitrarily ruled out the possibility that they would be able to corroborate the opponent's allegations. Pre-empting the evidence's evaluation in this manner had been unjustified. See also T 2238/15.

Similarly, in T 906/98 the board found that the opposition division had applied the wrong criteria when exercising its discretion (not to order the hearing of witnesses on a prior use) by speculating instead of investigating before refusing to take the evidence on offer, which related to the aspect of the prior use in dispute, namely what had been used and so made available to the public.

The appellant in T 1028/11 alleged that the opposition division had infringed its right to be heard, and so committed a procedural violation, by refusing to hear the witness it had offered. The board disagreed: a witness's function was, in essence, simply to corroborate the alleged facts on which they were heard and not to fill in gaps in those facts. Parties therefore had to specify what legally relevant facts the witness's testimony was intended to prove. Based on the evidence available, the opposition division had taken the view that the public prior use was not prejudicial to patentability. The board found that there would have been little point in hearing the witness at that stage. Cited in T 444/09.

In T 2003/08 of 31 October 2012 date: 2012-10-31 witnesses were summoned in accordance with R. 118 EPC and they were invited to confirm their attendance. Neither witness replied at all. But both witnesses were present. The appellant (patentee) requested the board to refrain from hearing them. The failure to react to the invitation in the summonses did not have any influence on the board's view that the witness evidence was necessary.

In T 361/00 the board ruled that there was no point hearing the author of statutory declarations as a witness at oral proceedings because, in view of the other aspects on file that had been discussed, it would not change its decision. Nor did the board agree that the opposition division had committed a substantial procedural violation by ignoring an offer to present the witness: the minutes of the oral proceedings – which the party concerned had not contested – did not record that it had made such an offer.

According to the case law of the boards of appeal and as mentioned in decision T 142/97 (see point 2 of the Reasons), a deciding body must ascertain the relevance of evidence submitted to it before deciding to admit or reject it. When relevant features of the prior art trailers as asserted by the opponents were questionable and remained contested, a request by the opponents for the evidence to be secured, e.g. by hearing witnesses proposed by the opponents or by inspection of the trailer in accordance with Art. 117(1)(f) EPC, could not be rejected without justification. In case T 1647/15 the opposition division had rejected the evidence on the basis of mere suppositions, making no real attempt to definitely assess it or its relevance. Only if the opposition division knew enough about the evidence offered to ascertain that it was not relevant, would it have been justified in rejecting it. Because the opposition division did not grant the request for inspection on this issue, the right to be heard was violated. This refusal to consider evidence filed in due time infringed a party's fundamental rights to a free choice of evidence and to be heard (Art. 117(1) and 113(1) EPC).

In T 1872/08 the board decided that in not admitting the additional comparative tests offered by the patentee, the opposition division had not taken into account that the patentee deemed further comparative data to be absolutely necessary in order to overcome its objections as to inventive step. The opposition division had thus deprived the patentee of the possibility to defend its case effectively. See also T 2294/12, in which the examining division had disregarded comparative tests.

While it is well-established by case law that third-party observations (and accompanying evidence) can be considered, both at first instance and on appeal, there is no obligation on the board beyond such consideration and no right of a third party to be heard (T 390/07). As a rule, third parties have none of the procedural rights associated with status as a party to the proceedings, in particular the right to be heard (T 1756/11). Conversely, parties to the proceedings can comment at any stage on new facts and evidence emerging from third-party observations filed after expiry of the opposition period, if they think that these could influence the decision (T 1756/11; see also chapter III.N. "Third-party observations").

In G 4/92, concerning the case of a decision taken against a party who has been duly summoned but fails to appear at oral proceedings, the Enlarged Board established that new evidence may not be considered unless it has been previously notified and merely supports the assertions of the party who submits it, whereas new arguments may in principle be used to support the reasons for the decision (G 4/92, OJ 1994, 149, headnote 2). For more on non-attendance at oral proceedings, see chapter III.C.5.

In R 21/09, the party alleged an infringement of the right to defence on the basis that the board had refused to allow further discussion of all the documents submitted to the English courts. In the end, the Enlarged Board did not allow the petition.

See also chapter III.B.1. "Right to be heard".