Several decisions of the boards of appeal considered in greater detail, when examining the admissibility of the opposition, what constitutes sufficient substantiation in the notice of opposition.
In T 134/88 the opposition did not deal with all the features of the contested claim, but still satisfied the requirements of R. 76(2)(c) EPC (former R. 55(c) EPC 1973). The board summed up by saying that an opposition directed against alleged lack of inventive step in the case of a combination invention was generally inadmissible if it related only to the assessment of one individual feature - to be admissible, it would have to deal with the invention as a whole, or at least with its essential content, so that when the facts on which the opposition was based were indicated, circumstances became recognisable which enabled the patent proprietor and the assessing body to pass conclusive judgment on the asserted grounds for opposition without having to make enquiries of their own. Allegations which could not be subsumed under one of the opposition grounds have to be left out of consideration (see also e.g. T 1279/05, T 114/07, T 521/00, T 1074/05). A detailed and exhaustive discussion of matters which were implicit to such skilled persons was not needed to understand the opponent's case and, therefore, not an admissibility requirement (see also T 534/98, in which it was held, with reference to the prevailing view in the case law, that substantiation of an opposition did not require proof of a claim concerning common general knowledge, unless the claim was called into question by another party or by the EPO).
In T 1014/09 the opposition was based on the inadmissibility of an amendment "because it was not covered by the original disclosure". The board had to establish to what extent this general reference to the original disclosure could be regarded as a due indication of the facts, evidence and arguments within the meaning of R. 76(2)(c) EPC, and to what extent the assessment of the amendment to the claims could be construed as an indication that the amendment had unlawfully changed or extended the technical information. The board concluded that the facts of the case at issue and the accompanying legal analysis set out in the notice of opposition had to be regarded as duly substantiating the ground for opposition under Art. 100(c) EPC.
In T 185/88 (OJ 1990, 451) the board ruled that grounds for opposition were in due form if the only document cited in support of the sole assertion of lack of inventive step (in this case a German patent specification), although actually published after the date of filing or priority, nevertheless contained a reference to a publication known before the date of filing or priority - in this case a German unexamined application or "Offenlegungsschrift" (cf. the different circumstances in T 864/04).