3.3.4 Improper reasons for rejection of evidence offered

If a disputed point is highly relevant to the validity of the contested patent, it is, as a rule, not in keeping with good procedural practice for an opposition division not to take up an opportunity to hear a witness or party in evidence and instead to require written statements and make do with their typically lower probative value. The board in T 329/02 could not identify any extraordinary circumstances that might have justified an exception to this rule in the case in point.

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.

In T 314/18 (alleged public prior use – several sales) a witness had been offered but not heard. Contrary to the view of the opposition division, the appellant (opponent) had offered the witness solely to corroborate the facts already submitted in support of the alleged prior use. No provision of the EPC required an alleged prior use to be conclusively proven within the opposition period. In referring to the Guidelines and arguing that the lack of adequate substantiation of the prior use in the notice of opposition could not be overcome by hearing the witness, the opposition division had mixed up the submission of facts and the proof required to establish them. By refusing to hear the proposed witness, the opposition division had in fact proceeded to assess evidence that had not yet been established, although it had appeared to be prima facie relevant for the decision to be taken. This was procedurally incorrect and the opposition division had thus infringed the appellant's right to be heard under Art. 117(1) and 113(1) EPC.

According to the case law of the boards of appeal and as mentioned in decision T 142/97, 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. 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).

More recently, the board in T 1738/21 decided that by not hearing the witnesses offered, the opposition division had violated the appellant's basic procedural rights under Art. 117(1) and 113(1) EPC, namely that a party can give evidence in an appropriate form and have that evidence heard. The board noted that it was established case law that an opposition division violates an opponent's right to be heard under Art. 113(1) EPC if witnesses have been offered in connection with the disclosure of certain features of an alleged public prior use considered as adequately substantiated, but the opposition division decides that the alleged public prior use does not constitute novelty-destroying state of the art without hearing the witnesses. Therefore, if witnesses have been offered to corroborate alleged facts which were decisive for the decision to be taken, then the opposition division should hear the witnesses regarding the alleged facts in order to be in a position to take a decision on the basis of all the available evidence. The board considered therefore which alleged facts the appellants intended the witnesses to corroborate and if these facts were decisive for the outcome of the decision under appeal and the board came to the conclusion that the witnesses who had been offered, were in a position to corroborate the alleged facts which were found not convincing by the opposition division. The board could find no mention in the decision under appeal of the appellant's offer of witnesses nor any indication of the opposition division's reasons for not hearing those witnesses. The opposition division's failure to hear at least three witnesses amounted to a serious procedural violation.

In T 2517/22 appellant 2 had offered Mr R as a witness already in the notice of opposition and again in their reply, after the patentee had questioned the probative value of the affidavit D2a (affidavit of an employee of appellant 2). In the annex to the first summons, the opposition division considered D2a to be sufficient evidence for public availability of D2 (operating manual) and did not summon Mr R as a witness. The opposition division changed its mind however and announced that D2 was not part of the prior art, albeit without taking into account the previous offer to hear a witness on the topic. In the board's view, the statements in the affidavit D2a represented facts which were a priori of high relevance for establishing whether or not D2 was part of the prior art, and therefore of high relevance for the outcome of the opposition proceedings. An offer to hear the undersigned of the affidavit D2a as a witness represented a further relevant and appropriate offer of evidence for the facts. The board stated it was a party's choice to present whatever means of evidence it considered to be suitable and it was an opposition division's duty to take its decision on the basis of all the relevant evidence available rather than to expect the presentation of more preferred pieces of documentary evidence, and to speculate on the reasons for and draw conclusions from their absence. The opposition division was of course free to evaluate any evidence provided by a party, but this freedom could not be used to disregard evidence that had been offered, and which might turn out to be decisive for a case, in particular not with the argument that some better evidence would have been expected. Instead of accepting the evidence offered by appellant 2, the opposition division appeared to have based its decision on general assumptions made on the capability of persons to recollect events after a certain time period (15 years) and specific assumptions made on the witness's personal capability, knowledge and experience. By making these assumptions without hearing the offered witness, the opposition division had in fact assessed evidence without examining it. A sufficiently exact recollection of various events 15 years later should not have been denied beforehand. The board concluded that the failure to consider appellants 2’s offer to hear a witness on the public availability of D2 constituted a substantial procedural violation of the right to be heard. Reference was made to T 906/98 and T 474/04.

In T 267/06 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 (drawing without a date). 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. See also T 660/16.