The long-running issue of poisonous priority, and in particular poisonous divisionals, began with decisions such as T 1496/11, in which the EPO Board of Appeal found that an embodiment described in a divisional application was novelty-destroying for claim 1 of the parent application, because the divisional was entitled to an earlier priority date. The full story of the Board’s decision in this case can be read in our previous article.

To recap briefly, in interlocutory decision T 557/13 dated 17 July 2015, the Technical Board of Appeal referred five questions to the Enlarged Board of Appeal (as G 1/15), seeking clarification of how Article 88(2), second sentence, EPC is to be applied in the light of G 2/98 (which dealt with the requirements for claiming priority of “the same invention” and the issue of claims entitled to “partial priority”) in the case of a generic “OR”-claim, and whether parent and divisional applications may be prior art under Article 54(3) EPC against one another in respect of subject matter disclosed in a priority application but not entitled to priority.

A generic “OR”-claim was defined as a claim directed to subject matter defined by one or more generic expressions, such as a chemical formula, a continuous range of numerical values or a functional definition, or otherwise. Such a generic “OR”-claim encompasses, without spelling them out, alternative subject-matters having all the features of the claim. “Partial priority” was used to refer to a situation in which part of the subject matter of a claim is entitled to the priority date of a single earlier application, whereas the remaining subject matter of the claim is entitled only to the filing date of the subsequent European patent application.

The first of the five questions referred by T 557/13 was:

  1. Where a claim of a European patent application or patent encompasses alternative subject matters by virtue of one or more generic expressions or otherwise (generic “OR”-claim), may entitlement to partial priority be refused under the EPC for that claim in respect of alternative subject matter disclosed (in an enabling manner) for the first time, directly, or at least implicitly, and unambiguously, in the priority document? (emphasis added)

Such was the anticipated importance of the G 1/15 referral that all proceedings before examination or opposition divisions, where the outcome depended entirely on the outcome of G 1/15, were stayed on 2 October 2015.

On 29 November 2016, the Board issued the answer to this first question:

“Under the EPC, entitlement to partial priority may not be refused for a claim encompassing alternative subject matter by virtue of one or more generic expressions or otherwise (generic “OR”-claim) provided that said alternative subject matter has been disclosed for the first time, directly, or at least implicitly, unambiguously and in an enabling manner in the priority document. No other substantive conditions or limitations apply in this respect.” (emphasis added)

In other words, publication of the priority document in which the alternative subject matter is disclosed cannot be novelty-destroying under Article 54(3) EPC for the later application, where the generic “OR”-claim is entitled to partial priority.

Since the answer to the first question was “no”, the Board found it unnecessary to answer the remaining four.

The reasons for the decision were finally published on 2 February 2017. The following is a brief summary of some of the more interesting points.

Firstly, in reason 4.2 the Board points out that as a matter of principle, where a right is established by an international treaty or convention, or by national law, it cannot be restricted by imposing supplementary conditions in administrative rules or guidelines or even in jurisprudence.

Further, in reason 4.4 the Board concludes that the right of priority operates to exclude the collision of subject matter disclosed during the priority period with identical subject matter disclosed in a priority document, in so far as priority has been validly claimed.

With regard to Article 88(3) EPC (“If one or more priorities are claimed in respect of a European patent application, the right of priority shall cover only those elements of the European patent application which are included in the application or applications whose priority is claimed”) the Board states in reason 5.1.2 that the term “elements” is not to be understood as a single feature, but as subject matter such as that defined in a claim or disclosed in the form of an embodiment in the description.

As a consequence, the proviso laid down in G 2/98 (ie that the use of a generic term or formula in a claim for which multiple priorities are claimed is acceptable provided that it gives rise to the claiming of a limited number of clearly defined alternative subject-matters) cannot be construed as implying a further limitation of the right of priority.

Reason 6.4 of the decision goes on to explain how the partial priority of a generic “OR”-claim should be assessed. This can be summarised as follows:

Step 1: determine the subject matter disclosed in the priority document that is relevant, in respect of prior art disclosed in the priority interval, in accordance with the disclosure test laid down in G 2/98 (ie the skilled person must be able to derive the subject-matter of the claim directly and unambiguously, using common general knowledge, from the previous application as a whole). Explanations put forward by the applicant or proprietor to support its claim to priority, to show what the skilled person would have been able to derive from the priority document, may also be used.

Step 2: Examine whether this subject matter is encompassed by the claim of the application or patent claiming said priority. If the answer is yes, the claim is de facto conceptually divided into two parts:

  1. the part corresponding to the invention disclosed “directly and unambiguously” in the priority document; and
  2. the remainder, which is not entitled to this priority, but which itself gives rise to a right to priority.

The Board notes in reason 6.6 that the above determination is common practice in the EPO and as such should not pose any additional difficulty or give rise to uncertainty for third parties. Decisions such as T 665/00, T 135/01, T 571/10 and T 1222/11 show that it can be carried out without the need for additional tests or steps. In reason 6.7, the Board confirms that, as a result, the assessment of entitlement of a claim to partial priority right does not have any further requirements.

Finally, in reason 6.5 of the decision, the Board points out that the above corresponds, logically and exactly, to the FICPI Memorandum of 1973, which can be assumed to express the intent of the legislator and which concerns multiple and partial priorities, which states that: “If a first priority document discloses a feature A, and a second priority document discloses a feature B for use as an alternative to feature A, then a claim of the application directed to A or B will in fact consist of two distinct parts A and B respectively, each complete in itself...”, and further: “... it would be appropriate to claim a partial priority in situations corresponding to the “OR” situation under Multiple Priorities”, the European patent application itself taking the place of the second priority document.

Conceptual splitting of a generic “OR”-claim, as outlined by the Board, allows for the assignment of a priority date to a part of a generic claim, even though that part is not literally disclosed in the priority document. This would seem to put the issue of poisonous priority, and poisonous divisionals, to bed once and for all.