For some years patent practitioners have been alarmed by the possibility that dividing an application might have the consequence that the divisional application can become a novelty destroying reference for the parent application or vice versa. Decision T 1222/11 may have shown the reason for this apparent paradox.
In epi Information 2/2011, 54, the article “Poisonous EPC Divisionals” was published. It addresses (see p. 61, annex 1) the situation that in a first application an invention is disclosed in general terms (here indicated as ABC) and a European application claims the priority of the first application. The European application is divided and in the parent application a more limited version (ABC1) is claimed which is not disclosed in the priority application. However, the priority application contains a specific example (ABC2) falling within the limits of the claimed subject matter of the parent application (ABC1). The description of all three applications is identical. It is suggested that the limited claim (ABC1) in the parent application is not entitled to the priority of the first application whereas the more specific example in the description of the divisional application (ABC2) enjoys this priority. The conclusion is drawn that the divisional application is a conflicting application within the meaning of Article 54 (3) EPC and destroys the novelty of the subject-matter claimed in the parent application.
Recent decisions of the EPO (T 1496/11 of September 2012, not published, and of the English Patents Court (Nestec SA v Dualit Ltd,  EWHC 923) have shown that there is a real danger in this concept and have entailed many reactions in blogs and literature. Both decisions are concerned with situations in which the subject-matter in the European application was not limited but generalized in comparison with the priority application. The conclusion, however, was the same. There was no valid priority for the amended claim and the specific example in the priority application anticipated the amended claim, in T 1496/11 based on the concept of poisonous divisionals, in Nestec SA v Dualit Ltd as a consequence of the publication of the priority application which was a European application.
Why is the concept of poisonous divisionals paradoxical? In 1925, the right to file divisional applications was introduced into the Paris Convention in order to save the applicant from the loss of originally disclosed subject-matter which he cannot pursue in the framework of a pending application for a formal reason, i.e. lack of unity. This legal purpose makes clear that the division of an application is in no way intended to impair the applicant’s right to the patent and has nothing to do with the requirements for patentability. The right to file a divisional application of the applicant’s own volition was later added. Article 4 G of the Paris Convention stipulates for both situations that the applicant preserves as the date of the divisional application “the date of the initial application and the benefit of the right of priority, if any”. This wording is taken up to the same effect in Article 76 EPC according to which “the divisional application shall be deemed to have been filed on the date of filing of the earlier application and shall enjoy any right of priority”. It seems that the legislators of the Paris Convention and of the EPC wanted to express in this way that both applications have the some valid dates for their respective subject-matter. Thus, one might assume that they have to be treated in respect of the relevant prior art in exactly the same way. This would coincide with the purpose of a divisional application being of a mere formal character and having no consequences for the assessment of the requirements of patentability.
Why does T 1496/11 come to different conclusions? The reason is that the assessment of the right of priority for the parent and the divisional application is made in different ways. For the specific example in the description, the priority is accepted whereas for the same example as an integral part of the claim to be examined, it is not accepted. Decision T 1496/11 confines itself to the statement that the claimed device has been generalized to include embodiments not disclosed in the priority document and thus does not constitute the same invention as that set out in the priority document. It does not even mention the possibility of a partial priority for the allegedly novelty destroying specific embodiment.
Nestec SA v Dualit, dealing with the same priority problem in the relation between a first European application and a second European application claiming the priority of the first, is more specific and, citing Novartis AG v Johnson Medical Ltd  EWHC 1671, the Court states:
“I discern from this passage that the EPO considers it is permissible to afford different priority dates to different parts of a patent claim where those parts represent a limited number of clearly defined alternative subject-matters and those alternative subject-matters have been disclosed (and are enabled) by different priority documents. Further, this principle applies even if the claim has adopted a generic term to describe and encompass those alternatives.” The cited passage itself is referring to G 2/98 where the Enlarged Board of Appeal stated in pt. 6.7:
“The use of a generic term or formula in a claim for which multiple priorities are claimed in accordance with Article 88 (2) EPC, second sentence, is perfectly acceptable under Articles 87 (1) and 88 (3) EPC, provided that it gives rise to the claiming of a limited number of clearly defined alternative subject-matters.”
This was interpreted by some decisions of the Boards of Appeal to mean that a continuum of a numerical range of values did not correspond to distinctive alternative embodiments. If no separable alternative embodiments could be identified within that continuum, the subjectmatter of the contested claim as a whole was not entitled to the claimed priority date (T 1877/08, cited in Case Law of the Boards of Appeal, 7th ed. 2013, II.D.4.3). Following this case law, the Patents Court, finding that the broadened part of the claim covers a whole range of arrangements, denies a partial priority for the specific example.
T 1222/11, in a long obiter dictum, expressly disagrees with T 1877/08 and similar decisions. The Board notes that the assessment required by Article 88 (3) EPC, as to which elements (alternatives) of a claim are covered by any of the multiple priority claims can be achieved only by a comparison of the claimed subject-matter of that claim with the disclosure of the multiple priority documents. Therefore, in the context of assessing which alternatives of a contested claim are covered by any of the multiple priority documents, the words "gives rise to the claiming of a limited number of clearly defined alternative subject-matters" refer to the ability to conceptually identify by said comparison a limited number of clearly defined alternative subject-matters to which the multiple rights of priority claimed can be attributed or not. This is obviously necessary in order to identify which parts of the claims benefit from the effect of the priority right defined in Article 89 EPC.
In addition, the Board refers to the document in the Travaux préparatoires to the EPC cited in G 2/98 in respect of partial and multiple priorities, i.e. the FICPI Memorandum (Munich Diplomatic Conference, Doc. M 48/I, Memorandum C) which gives as an example for the concept of multiple priorities that a first priority application discloses a narrow chemical formula and a second priority application discloses a broader chemical formula within its scope including the narrower formula. The Memorandum states that in an application claiming both priorities, it would suffice to draw up a single claim directed to a compound defined by the broad formula. This claim would enjoy priority from the first priority date to the extent that the compound comes within the scope of the narrow formula, and the second priority for the rest of its scope. The Board cites two other examples given in the Memorandum for multiple priorities, the first concerning narrower and broader ranges and the second concerning specific and generic definitions in the mechanical field. The Board concludes that it is not necessary for the acknowledgement of the right of priority for a specific embodiment disclosed in the priority application to identify this embodiment in the claim of the European application as a separate embodiment. Thus, this embodiment cannot be novelty destroying if the claimed subject-matter has been generalized in the application or patent claiming the priority.
The poisonous divisionals approach prevents a reasonable use of divisional applications. Its origin was caused by an over-restrictive attitude of some Boards of Appeal towards partial and multiple priorities. The sentence in G 2/98 that multiple priorities are acceptable provided that they give rise to the claiming of a limited number of clearly defined alternative subject-matters has been interpreted out of context, neglecting the Enlarged Board’s of Appeal express statement that generic definitions are acceptable and without considering the purpose of partial and multiple priorities for which decision G 2/98 has taken recourse to the FICPI Memorandum cited above. This Memorandum clearly states that multiple priorities should avoid the need to file parallel claims, one for the subject-matter enjoying one priority and another one for the subject-matter enjoying the other priority. Precisely, remedies of this type have been suggested by commentators in order to avoid the trap of the poisonous divisionals: Drafting one claim for the specific embodiment and another one for the generic subject-matter disclaiming the specific embodiment. The possibility of avoiding the anticipation by a highly sophisticated claim drafting which is directed to the identical subject-matter should make clear that there is no substantive reason to deny protection. No legitimate interest has been shown why a partial priority should not be derived from an example in a priority application which is an embodiment within the limits of the claimed subjectmatter in the application or patent claiming the priority. Within the meaning of G 2/98, the specific example is one clearly defined alternative subject-matter; the other alternative is the generic rest of the claim which has only the filing date as its valid date. It is to be hoped that other Boards will follow T 1222/11.