2.3.1 General principles

Art. 113(1) EPC requires that decisions may only be based on grounds or evidence on which the parties concerned have had an opportunity to present their comments.

According to the Enlarged Board of Appeal (see chapter V.B.4.3.8 "Reasons for a decision allegedly surprising"), this implies that a party may not be taken by surprise by the reasons of a decision, referring to unknown grounds or evidence (R 3/13; see also T 1378/11). A purely subjective surprise, however, has no bearing on whether a party had an adequate opportunity to comment. "Grounds or evidence" within the meaning of Art. 113(1) EPC need not emanate from the board, it is sufficient if another party raises the objection (R 2/08). If the reason given in a decision corresponds to an argument put forward by the other party (see also T 405/94), the petitioner was aware of it and thus not taken by surprise (R 4/08, R 12/09 of 15 January 2010 date: 2010-01-15, R 8/14) unless the board clearly indicated that it regarded those arguments as not convincing (R 11/12).

In T 996/09 the board held that the right to be heard was a fundamental guarantor for the parties that proceedings before the EPO would be conducted fairly and openly (with further reference to J 20/85 and J 3/90) and was intended to ensure that the parties to the proceedings were not taken by surprise by grounds mentioned in an adverse decision (following T 669/90, T 892/92, T 594/00 and T 343/01; see also T 197/88, T 220/93). In T 435/07 the board held that the grounds on which a decision were based had to be communicated to the applicants in such a way that they were put in the position to defend their rights. An objection against the grant of a patent had to be raised in such a way that the applicants were able to understand its factual basis and to react accordingly without first having to guess what the examining division might have had in mind.

Although parties may not be taken by surprise by the reasons for a decision, it is also settled case law of the Enlarged Board of Appeal under Art. 112a EPC that a board of appeal is not required to provide the parties in advance with all foreseeable arguments in favour of or against a request. In other words, parties are not entitled to advance indications of all reasons for a decision in detail (see chapter V.B.4.3.5 "No obligation to provide detailed reasons for a decision in advance"). In T 1634/10, T 2405/10, T 1378/11 and T 1090/18 the boards explicitly applied this case law of the Enlarged Board of Appeal in relation to Art. 112a EPC to first instance proceedings.

In T 1065/16, lack of reproducibility as a ground for opposition had not been a subject of the opposition proceedings until the oral proceedings. It therefore amounted to a fresh ground for opposition and its introduction came as a surprise. In its summons, the opposition division had expressly stated that only novelty and the inventive step of claim 1's subject-matter were to be examined. As the patent proprietor had not been given sufficient opportunity to comment on this new ground for opposition, the opposition division had infringed Art. 113(1) EPC and thus committed a substantial procedural violation.

In T 2351/16 the board found that that the examining division had issued a decision of refusal after only one communication under Art. 94(3) EPC as such did not constitute a violation of the appellant's right to be heard (see also chapter IV.B.2.3. "Refusal after a single communication"). However, in its decision the opposition division had raised (for the first time) an additional argument in support of the division's objection, following the applicant's reply to the Art. 94(3) EPC communication. This constituted a violation of the applicant's right to be heard and, therefore, a substantial procedural violation.