The Enlarged Board of Appeal of the European Patent Office recently published an important decision (G1/15) on an issue related to priority claims.

The issue of poisonous divisional applications is one that has caused concern before the European Patent Office for some time. The term “poisonous divisional” refers to a situation where a divisional application becomes citable as prior art against its parent application (or vice versa). This can arise where different subject-matter in the two applications are adjudged to have different priority dates. Often this is as a result of attempting to claim an invention more broadly in a subsequent application than was disclosed in the priority application. A similar problem can arise with so called “poisonous priorities”. This term refers to a situation where a priority application which has published becomes citable as prior art against a subsequent application claiming priority from it because a claim in the subsequent application is found not be entitled to the claimed priority date.

A particular area of doubt has been the entitlement to priority of claims which cover alternative subject-matter and especially where the alternatives are not expressly stated but implied, for example by use of a generic term.  These types of claims are referred to as generic “OR” type claims.  Since generic “OR” claims cover alternative subject-matter, each alternative could potentially be entitled to its own priority date. This is known as “partial priority”.

In an earlier decision G 2/98, the Enlarged Board of Appeal indicated in that partial priority can be attributed where a generic “OR” claim gives rise to a limited number of clearly defined alternative subject-matters (Reasons point 6.7, last sentence). In subsequent decisions, some Technical Boards of Appeal have interpreted this strictly as an additional requirement to be met and denied partial priority whilst others treated claims to partial priority more leniently. Denying the right to partial priority can have a significant impact resulting in a claim being found invalid as a result of a poisonous divisional/priority.

This issue was brought before the Enlarged Board of Appeal as a series of questions relating to partial priority and poisonous divisionals more generally. In their decision, the Board has only provided an answer to the first question which sought clarification of the requirements for entitlement to partial priority of generic “OR” type claims. Since the Board’s answer to the first question rendered the rest of the questions irrelevant, they were not considered in detail.

The first question put to the Board reads as follows:

‘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 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?’

The board answered “no” to this question, indicating that the proviso laid down in G 2/98 cannot be construed as implying a further limitation of the right of priority.

The upshot of this is that entitlement to partial priority for generic “OR” type claims is to be assessed more liberally than some of the previous decisions of the Technical Boards of Appeal had indicated. This should effectively put an end to poisonous divisional attacks. The decision will also be of assistance in overcoming poisonous priority attacks, at least where the priority application published after the subsequent application.

If you have any questions or require any further information on poisonous divisionals or priorities please get in touch with one of our attorneys who will be happy to advise you.