Practical implications of G1/15

“Poisonous priorities” and “toxic divisionals” involve the potential prior art effect of unpublished documents (referred to as Article 54(3) documents in EPO practice). In summary, the Enlarged Board held in G1/15 that a generic claim encompassing alternative subject- matter may not be refused partial priority, provided that the alternative subject-matter has been directly and, at least implicitly, and unambiguously disclosed in the priority document. By endorsing a generous approach to partial priority, the Enlarged  Board effectively ruled out European patents being invalidated by so-called “poisonous priorities” and “toxic divisionals” but at the same time the Enlarged Board’s decision has affected other circumstances, and we look at such a scenario in this article.

In particular, we look at the effect this decision has had on the assessment of inventive step in which prior art has been published between the priority date and the filing date of a European patent/patent application.

As background, partial priority now arises where the priority document discloses a feature, e.g. the range 4-6, and the subsequent application is broadened to disclose the range 1-10. Following G1/15 in assigning priority, the claim is split into two notional parts: the first specifying the range 4-6 as disclosed in the priority document and the second specifying the range 1-10 punctured by the range 4-6, i.e. ‘1-3 & 7-10’. The first part is assigned the filing date of the priority document; the second part is assigned the filing date of the subsequent application.

Before G1/15, partial priority for the claimed range of 1-10 could have been denied in its entirety, on the basis that the broader range was not disclosed in the priority document. There would have been no account taken of the narrow range 4-6 disclosed in the priority document. The effective filing date of a claim referring to the range 1-10 would be the filing date of the subsequent application.

Now assume that there exists a prior art document disclosing the range 4.5-5.5 that was published between the filing date of the priority document and the filing date of the subsequent application. Before G1/15, the subsequent application directed to a range of 1-10 would lack novelty over this prior art document since the claim of the subsequent application would not benefit from any claim to priority. However, assigning partial# priority in line with G1/15 the claim of the subsequent application would be novel; the part of the claim that the prior art in theory anticipates benefits from the filing date of the priority document. Accordingly, the prior art document is not citable against the part of the claim to which it would be relevant, and the claim is novel.

In cases involving “toxic divisionals” and “poisonous priorities”, this tends to be the end of the matter since the prior art documents involved are post-published documents, i.e. published after the filing date of the subsequent application, and under EPO practice are not citable for the purpose of assessing inventive step. In contrast, in the scenario set out above the prior art document is an intermediate document, i.e. published between the filing date of the priority document and the filing date of the subsequent application. As a result, the prior art document is citable for the assessment of inventive step for subject-matter that does not validly claim priority. In this case, that is the part of the claim directed to the range ‘1-3 & 7-10’. Hence, applying partial priority in line with G1/15 overcomes any potential novelty objections, but the prior art document is still citable for the assessment of inventive stepa gainst at least part of the claim.

Given the circumstances of the present situation, it is possible, perhaps likely, that the majority of the application’s examples fall within the narrow range, i.e. the range 4-6, disclosed in the priority document. It is also possible that the application contains not a single example falling within the part of the claim now being assessed for an inventive step, i.e. the part of the claim directed to ‘1-3 & 7-10’. In the absence of example in the “claimed range”, an applicant may find it difficult to argue that the claimed invention is based on a surprising, unexpected improvement in performance. Instead, in the context of the EPO’s problem solution approach, the technical problem addressed by the claimed invention may have to be formulated less ambitiously as the provision of a mere alternative. Although G1/15 may help applicants overcome novelty objections, they may still face difficulties overcoming inventive step objections.

On the other hand, applying partial priorities in the scenario set out above may have a different impact on opposition strategy. When formulating an opposition (or invalidity action), it is common to look for prior art that anticipates or corresponds as closely as possible to the “heart” of the claimed subjectmatter. For example, demonstrating that the preferred embodiments of any patent either lack novelty or inventive step is a good starting point for an opposition. In turn, the preferred embodiments of an application are often closely associated with the disclosure in the priority application. Focussing on prior art that relates closely to the preferred embodiments (and in turn relates closely to the disclosure of the priority document) could be ineffective if a scenario set out above involving partial priorities occurs.

For example, an intermediate prior art document, i.e. published between the filing date of the priority document and the filing date of the subsequent application, would only be citable against subject-matter not benefiting from the filing date of the priority document. If that priority document discloses only the preferred embodiments of the claim which in the subsequent application are entitled to claim priority back to the filing date of the priority document, the claim would not lack novelty. Instead, an opponent would need to rely on an inventive step attack directed against the subject-matter that is not entitled to claim priority. Any such inventive step attack would start from the disclosure in the intermediate prior art document. In reply, a patentee can argue that it would not have been immediately obvious to modify the prior art from within the narrow range to outside the narrow range. At the EPO, a patentee will find such arguments much easier after grant at which time the full burden of proving that the claims are obvious falls to the opponent.

How can we avoid such scenarios? First, from a patentee’s perspective you should always be aware that a claim can be assigned partial priorities and when intermediate prior art documents have been cited against your application or patent, highlighting these partial priorities may be a useful way of overcoming the cited prior art. From an opponent’s perspective, if relevant intermediate prior art has been identified in a search and that prior art is relevant only to the preferred embodiments of the granted patent, it would be advisable to carry out further searching, looking for disclosures relevant to the area of the claims that had been added when filing the
subsequent application. Prior art documents disclosing subjectmatter relevant to the extended area of the claim may on the face of it look less relevant than the prior art disclosing the preferred embodiments of the granted patent but ultimately may be more useful when formulating an inventive step attack.

In conclusion, although G1/15 addressed the issues of “toxic divisionals” and “poisonous priority” and made it clear that such issues should not occur, the Enlarged Board’s decision also fundamentally affects how the EPO approaches the way priority is assigned to different areas/parts of the claims. The relevance of this clarification will affect cases in different ways depending on the facts and circumstances of each. It is however something of which patentees/ applicants and opponents, should be aware.