For cases in which the amendment consists of the replacement or removal of a feature from an independent claim, the boards occasionally apply the essentially or the three-point test. This test is also set out in the Guidelines H‑V, 3.1 - 2015 edition. In case T 2311/10, however, which concerned an intermediate generalisation, the board expressed the view that the three-point or essentiality test was unhelpful or even misleading (see also T 1118/10; compare also Guidelines H‑V, 3.2.1 - June 2012 edition, which referred to the essentiality test in the context of an intermediate generalisation, and later versions, which no longer do). The board in T 755/12 pointed out that, although some tests such as the essentiality test have been used as an aid in assessing the allowability of amendments, they could not replace the need to answer the question of what a skilled person would objectively have derived from the description, claims and drawings of a European patent application on the date of filing (G 3/89, OJ 1993, 117, see in this chapter II.E.1.2.1 "Gold standard: directly and unambiguously derivable" above).
In T 331/87 (OJ 1991, 22) the board held that the replacement or removal of a feature from a claim might 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 might be inessential even if it was incidentally but consistently presented in combination with other features of the invention (frequently cited, see for example, T 708/07, T 775/07, T 747/10; but see also T 910/03 where the board criticised, in the light of G 2/98 (OJ 2001, 413), the distinction made between essential and non-essential features).
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. See also T 496/90, T 415/91, T 628/91, T 189/94 and T 728/98 (OJ 2001, 319; concerning the deletion of the feature "substantially pure"). See also T 2202/08, in which the board referred to the test in T 260/85 and observed that it might not always be necessary or expedient to apply the test employing the three criteria of T 331/87 in a case as simple as the one at issue.
The board in T 648/10 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 could 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 T 404/03 the board considered that the decisions of the boards of appeal describing and using the current palette of "tests" in connection with various types of amendments might lead to some confusion. As far as the disclosure of a group of features was concerned, as distinguished from their scope, the generalisation of a feature in a claim and the isolation of features from embodiments in the description essentially both involved a deletion of a feature, namely the specific feature and the remaining features of the embodiment respectively. The board therefore considered that these cases could be subject to the same criteria as a pure deletion, and hence, in principle, the three point test. Rather than requiring a specific statement or suggestion in the original disclosure, the three point test was more generous to the applicant because it essentially allowed the deletion of a feature if the skilled person realised from the common general knowledge in that field that the feature had nothing to do with the invention. Moreover, in the board's view, the cases of deletion of features and addition of features had to be distinguished with respect to the allowability of amendments under Art. 123(2) EPC 1973, since the former only removed elements that were originally disclosed and hence might be judged by a skilled person to be inessential to the invention, whereas the latter added new elements lacking any basis whatsoever in the original disclosure (see also T 2359/09, which applied the three-point essentiality test, having regard to T 404/03 and T 331/87, OJ 1991, 22).
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.
In T 628/91 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 236/95 the board held that if the problem could not be solved without the features concerned, they could not be considered unimportant.
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.
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.
In T 583/93 (OJ 1996, 496) the board held that any attempt to interpret Art. 123(2) EPC 1973 such that the introduction into a claim of features previously described as non‑essential would not be permissible, had to fail. 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.
In T 211/95 the examining division had refused a divisional application on the grounds that a set of features from the original claim of the parent application was entirely missing from the claim of the divisional application. The board was unable to accept this. It held that the requirements under Art. 76(1) EPC 1973 would be met if it was obvious for the skilled person that there were two technically unconnected teachings which could be claimed separately, and if the skilled person clearly saw that the set of features according to the subject-matter claimed in the parent application was not essential to the subject-matter claimed in the divisional application. In the case at hand, the subject-matter of the divisional application was directly and unambiguously disclosed in the parent application. On the issue of two technically unconnected teachings, see also T 341/06.
In T 2300/12 the board held that the purpose of the essentiality test was to ascertain whether the replacement or removal of a feature in an originally filed independent claim resulted in an extension beyond the content of the application as originally filed. In the case at issue, however, the granted claim was for a process, whereas there had been no such process claim in the set of claims originally filed. For that reason alone, the essentiality test could not be directly applied to establish whether there had been such an inadmissible extension.