In G 1/03 (OJ 2004, 413) the Enlarged Board held that, when anticipation was taken to be accidental, this meant that it appeared from the outset that the anticipation had nothing to do with the invention. Only if this was established could the disclaimer be allowable (see also order in G 1/03, according to which an anticipation is accidental if it is so unrelated to and remote from the claimed invention that the person skilled in the art would never have taken it into consideration when making the invention).
In T 500/00 the amendment was an undisclosed disclaimer introduced by the appellant into claim 1 during the examining proceedings in response to an objection of lack of novelty based on prior art document D1. The question that arose was whether or not the disclosure of D1 was accidental. In the case in point, the claimed solution showed an overlap with the teaching of D1. D1 and the application in suit concerned the same technical field, had, except for the disclaimed component, identical compositions and related to the same purpose of sufficient curing. Moreover, the same technical problem underlay both the patent in suit and D1. Since the skilled person would consider D1 as suitable prior art to make the invention, confirmed by the reference to D1 in the original application, the disclosure of D1 could not be considered as being accidental within the meaning of G 1/03. Furthermore, since D1 related to the same technical effect as the patent in suit, and since its starting polymers to be cured were structurally identical to those used in the claimed process, D1 could be considered as a suitable starting point for assessing inventive step.
The decision in T 14/01 concerned the allowability of a disclaimer aimed at removing an overlap with prior art in view of G 1/03. According to the board in this case, the allegation that a teaching extracted from prior art led away from the invention implied that the skilled person had taken this prior art into consideration. Yet for an anticipation to be accidental it was necessary that the skilled person would have never taken it into consideration. The board then decided that the prior art in question was not accidental in the sense of G 1/03, and that the disclaimer was not admissible.
In T 1297/12 document D3 itself was not unrelated and remote since it related to the same field as the patent in suit. However the appellant/patent proprietor argued that the specific novelty destroying disclosures in D3 were "unrelated and remote". The board cited T 14/01 and held that the fractions were disclosed in a relevant document, D3, and so could not be considered to represent an "accidental" disclosure. Thus, based on this assessment alone a disclaimer in respect of these disclosures would not be allowable. Even if one were, for the sake of argument, to follow the position of the appellant, the conclusion would be the same because the specific disclosures in question could not be considered to constitute remote or unrelated disclosures.
In T 1049/99 the board concluded that, contrary to what the respondent (patent proprietor) claimed, the skilled person would have taken the teaching of document D21 into consideration when working on the invention in search of a solution to the technical problem defined by the respondent, using appropriate and relevant means to resolve his problem in the same technical field as that of the patent in suit. Moreover, contrary to the respondent's conclusions at the hearing, the board stressed that the fact that a document was difficult to find in published prior art or was difficult for the skilled person to access was not sufficient to justify the conclusion that it constituted an accidental anticipation.
In T 217/03, on the issue of whether document D1 was an accidental anticipation, the board stated that D1 did not deal explicitly with the technical problem underlying the claimed invention. However, that was not decisive for accepting D1 as an accidental anticipation. The board concluded that D1 related to the same general technical field as that of the subject-matter of claim 10 and was not from a technical point of view so unrelated and remote that the person skilled in the art would never have taken it into consideration when working on the invention (see G 1/03, OJ 2004, 413). Thus the disclosure of D1 could not be considered to constitute an accidental anticipation. Therefore the disclaimer in claim 10 did not fulfil the conditions required to render it admissible.
In T 1146/01 the board held that comparative examples of D1, although teaching what not to do, nevertheless served to elucidate the teaching of the document as a whole and were closely related to the other experiments disclosed in the document. Although it could be said that a comparative example had a "negative relevance", it was neither remote from nor unconnected from the disclosure in the document. Thus, although the comparative examples of D1 provided a teaching not to be followed, this did not mean that their information was not part of the disclosure of D1 or would not be considered by an inventor working on his invention.
Other decisions too have had to establish whether or not the anticipation was accidental. In T 717/99, for example, the board did not agree with the opponent's conclusion that the anticipation was not accidental. In the following decisions, the boards ruled that the anticipation was not accidental and that the disclaimers were therefore inadmissible: T 1086/99, T 584/01, T 506/02, T 285/00, T 134/01 (field of pharmaceuticals, same illness; findings summarised by the board in T 1911/08, in which account was also taken of T 739/01, T 580/01 and T 639/01), T 351/12, T 632/12.