The appellant/patent proprietor having alleged that the opposition division had applied the wrong criteria for assessing compliance with Art. 123(2) EPC, the board in the recent case T 648/10 had an opportunity to reiterate the settled case law on the relevant test and confirmed that, where the replacement or removal of a feature from a claim is concerned, a feature consistently presented as an essential feature of the invention may not be deleted from an independent claim, since this would add subject-matter. However, it observed that the EPC does not require the use of any particular tests when assessing whether subject-matter has been added. Instead, such tests are tools which may be helpful, in certain situations, in the assessment of whether subject-matter has been added. In case T 2311/10, which concerned an intermediate generalisation, the board expressed the view, with reference to T 331/87 (OJ 1991, 22) and G 2/98 (OJ 2001, 413), that the three-point or essentiality test was unhelpful or even misleading (see also T 1118/10.).
Another test thus developed by the boards of appeal for the allowability of an amendment, having regard to Art. 123(2) EPC concerns the deletion of a feature. In T 66/85 (OJ 1989, 167) it was pointed out that if a technical feature was deleted from a claim in order not to exclude from protection certain embodiments of the invention, the broadening of the claim did not contravene Art. 123(2) EPC 1973 as long as there was a basis for a claim lacking this feature in the application as originally filed. It was immaterial whether or not the feature in question was relevant to the inventive concept of the claimed subject-matter (see also T 228/98).
T 133/85 (OJ 1988, 441) concerned a case where a feature was described as an essential feature of the invention but was not contained in the claim. The claim was therefore not supported by the description (Art. 84 EPC 1973). An amendment to the description to provide support for the claim was, however, not allowable under Art. 123(2) EPC 1973, because the amended description would contain subject-matter which extended beyond the content of the application as filed - namely information that such feature was not an essential feature of the invention.
On the other hand, in T 260/85 (OJ 1989, 105) it was stated that it was not permissible to delete from an independent claim a feature which the application as originally filed consistently presented as being an essential feature of the invention, since this would constitute a breach of Art. 123(2) EPC 1973. T 496/90, T 189/94, T 628/91 and regarding deletion of the feature "substantially pure", T 728/98 (OJ 2001, 319), confirmed this case law. In T 628/91, however, the disclosure was such that a structural feature could be replaced by a functional one, firstly because it was not disclosed as essential, secondly because its function was described.
In T 415/91, the board refused to allow the deletion of the feature "three-phase" alternating current. It argued that the low and high AC voltages were consistently referred to in the description and claims as being three-phase: the expression "three-phase" appeared about 200 times in the application as originally filed and no other number of phases was mentioned at all. The skilled person reading the application as originally filed would not necessarily have regarded the numerous references to "three-phase" as being purely by way of examples. Although it was possible that upon reflection, and using his imagination, it might occur to him that it was not essential to use three phases, this would be his own idea, resulting from his own thinking. It was not part of the content of the application as originally filed. In T 236/95 the board examined whether, considering the problem derivable from the original description, three deleted features were represented as essential features of the invention. If the problem could not be solved without the features concerned, they could not be considered unimportant.
That the original disclosure is the determining factor is also clear from T 331/87 (OJ 1991, 22), in which deletion of a non-essential feature was allowed: the replacement or removal of a feature from a claim may not be in breach of Art. 123(2) EPC 1973 if the skilled person would directly and unambiguously recognise that (1) the feature was not explained as essential in the disclosure, (2) it was not, as such, indispensable for the function of the invention in the light of the technical problem it served to solve, and (3) the replacement or removal required no real modification of other features to compensate for the change. The board also observed that the feature in question may be inessential even if it was incidentally but consistently presented in combination with other features of the invention (very often cited, see for example, more recently, T 775/07, T 1118/10., T 2311/10, T 747/10, and also T 60/90 dealt with above in II.E.1.6.2.d) "Elimination of contradictions").
Applying the above mentioned criteria in T 396/95, the board considered that whereas it was not expressly mentioned that the deleted feature ("carbonation") was essential for the invention this followed implicitly from the whole presentation of the invention. This feature was seen by the board to be indispensable for the function of the invention in the light of the technical problem it served to solve. Indeed the skilled person would not have regarded the carbonation feature as indispensable for the function of the invention, if the invention concerned the obtaining of chilled beverages and the problem underlying the invention consisted only of how to improve the cooling of the water in order to provide cooled beverages. But in the present case the application as originally filed related to "a water carbonator system" and the problem underlying the invention also comprised the improvement of gas/liquid mixing. In this case, the skilled person would regard the carbonation feature as indispensable for solving the problem underlying the invention.
In T 374/93 the opponent argued before the board that the amount of polymer to be added to the suspension as defined in claim 1 of the original application was an essential feature, and that the deletion of this feature was not allowable under Art. 123(2) EPC 1973. The board did not agree. In the case at issue, the deleted feature of the originally filed claim 1 appeared to be inconsistent with the teaching of the original application. In any case, in the board's view, the skilled reader would not immediately and unambiguously recognise from the passage containing several relative terms and expressions such as "in some instances", "e.g.", "normally" and "usually", that the feature as deleted from the original claim 1 was a mandatory feature.
In T 784/97 the patent proprietor alleged that a prior art document would have made the skilled person aware that the disputed feature was not essential. The board held that whether or not a feature of an independent claim had to be seen as "essential" could not be a question of the prior art disclosure. Rather, what had to be decided was what a skilled person was taught by the originally filed documents. In the present case, a skilled person having considered the originally filed documents was aware that the particle size was part of the alleged invention, so that this feature could not be omitted from an independent claim at a later stage without contravening the requirements of Art. 123(2) and Art. 100(c) EPC 1973.
Any attempt to interpret Art. 123(2) EPC 1973 such that the introduction into a claim of features previously described as nonessential would not be permissible, must fail. The board based this statement in T 583/93 (OJ 1996, 496) on the consideration that the Convention contained no requirement that forbade the redefinition of an invention provided that Art. 123(2) and (3) EPC 1973 were complied with. Such a redefinition was often necessary in order to take into account prior art not known to the applicant at the priority date. It was therefore possible that features described as optional at the priority date later became essential in the sense that they were necessary to delimit the invention from the prior art. The introduction of such features was permissible provided that, first, the application as originally filed contained an adequate basis for such limitations and, second, the resulting combination of features was still in line with the teaching of the application as originally filed.