EPO Enlarged Board of Appeal Prescribes an Antidote to Poisonous Divisionals

The EPO's Enlarged Board of Appeal has just provided (here) its detailed reasoning in response the questions concerning partial priority that were posed in referral G1/15. This full decision follows on from the brief answer that was provided in November 2016 (as reported here).

The central issue in this referral was the extent to which a narrow disclosure in a priority document may give rise to a right to partial priority, in the priority-claiming application, for a broader claim that encompasses the narrow disclosure. The Board concluded that the EPC contains no other requirements for recognising a right of partial priority except that the same invention as that disclosed in the priority document is encompassed by the claim of the priority-claiming application. This means, for example, that it is not necessary to consider whether applying a partial priority approach leads to the "claiming of a limited number of clearly defined alternative subject-matters" (wording derived from an earlier Enlarged Board decision, G 2/98, and the interpretation of which had led to divergent case law amongst the Boards of Appeal).

The Enlarged Board set out a two-step process for assessing whether partial priority can be enjoyed. The first step involves determining the relevant disclosure in the priority document. The second step involves determining whether this disclosure is encompassed by the claim in the priority-claiming case. If the answer is yes, then the claim is de facto conceptually divided into a part enjoying priority and a part not enjoying priority.

This welcome clarification means that most objections based on the so-called "poisonous divisional" theory, which rely on there being "other requirements" for enjoying partial priority, are unlikely to succeed. Similarly, there should now be much reduced risk of self-collision between a priority application that has been published and a later European patent application that claims priority to it. Nonetheless, it should be emphasised that careful drafting remains imperative in view of other complexities in European practice in this area, such as the EPO's strict interpretation of the "same invention" test for establishing a valid priority claim.