According to T 1536/08 it is well-established in the jurisprudence of the Boards of Appeal (J 7/82, T 94/84 and T 135/96) that the right to be heard enshrined in Art. 113(1) EPC also guarantees the right to have relevant grounds that could potentially influence the outcome taken into account in the written decision. A decision rejecting the opposition must therefore take into account the ground(s) for opposition raised as well as facts and evidence put forward in support of these grounds, including the cited prior art documents. Failure to consider evidence will normally constitute a substantial procedural violation of this fundamental right as it deprives the party of the right to have its case fully heard (see also T 1098/07). In the case at issue, the opposition division had completely ignored the unambiguous offer by the opponent in the notice of opposition to provide the original printed versions of crucial prior art documents. The failure to consider this offer constituted a violation of the right to be heard.
In T 1098/07 the board stated that 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. In the board's opinion, certain factors may nevertheless mitigate the severity of the violation. Thus, whether or not a failure of the decision to expressly mention material offered by a party in support of its case constitutes a substantial procedural violation will depend on the (prima facie) significance and evidential value of such material. Here the questions to be asked are: what facts is it intended to prove, how relevant is it to these facts and how likely is it that it will prove them? In the case at issue, given that the underlying issue was addressed, the failure to consider the evidence was a pardonable error that had not deprived the appellant of any fundamental rights.
In T 1110/03 the board held that Art. 117(1) EPC and Art. 113(1) EPC enshrined a basic procedural right generally recognised in the contracting states, i.e. the right to give evidence in appropriate form, specifically by the production of documents (Art. 117(1)(c) EPC), and the right to have that evidence heard.