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30 June 2017

G1/15: an antidote to poisonous priority and toxic divisionals

A decision has been issued by Enlarged Board of Appeal of the European Patent Office in case G1/15 clarifying the issue of how partial priority is to be assessed. This case concerned the related concepts of ‘poisonous priority’ and ‘toxic divisionals’ which have been the source of much debate over
the last few years. In G1/15, the Enlarged Board held that a generic claim encompassing alternative subject matter may not be refused partial priority, provided the alternative subject matter has been directly, at least implicitly, and unambiguously disclosed in the priority document. 

To qualify for a right of priority a European patent application must be filed in respect of the same invention as the earlier application. ‘Partial priority’ refers to a situation in which only part of the subject matter encompassed by a claim is entitled to the priority date. Partial priority can arise where the priority document discloses a feature A and the subsequent application has been broadened to include alternative feature B. In such a case a claim directed to A or B (an ‘OR’-claim) will be entitled to the priority date for part A of the claim and the filing date for part B of the claim.

The situation is less straightforward when a generic term C is used to encompass features A and B (a generic ‘OR’-claim). Such a situation can occur for example by the broadening of a chemical formula, of a range of values or of chemical compositions relative to the disclosure of a priority document. The Enlarged Board of Appeal has previously considered such a situation in G2/98 and had held that partial priority was allowed for a generic term or formula in a claim “provided that it gives rise to the claiming of a limited number of clearly defined alternative subject matters”. Following on from this decision two diverging lines of case law have arisen with some decisions taking a generous approach to partial priority and others applying a much stricter approach.

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