A recent referral in T0318/14 (Nestec S.A.) to the Enlarged Board of Appeal of the European Patent Office (EPO) seeks to clarify the extent to which the EPO can refuse to grant a patent application claiming subject-matter which is the same as subject-matter claimed in a European patent that has already been granted and which has the same effective filing date (a situation often referred to as ‘double patenting’).

It is established practice for the EPO to refuse to grant a patent if a European patent has already been granted for the same invention. Although the European Patent Convention (EPC) does not provide explicit basis for such a refusal, the EPO has historically relied upon the general provisions set out in Article 97(2) EPC and Article 125 EPC in combination with the Travaux Préparatoires to the EPC 1973. These provisions require the EPO to take account of the principles of procedural law generally recognised in the Contracting States of the EPC. Since it is generally recognised in the Contracting States that a person can be granted only one patent for an invention when the patents have the same filing date, the EPO has applied the same principle to European patents. The prohibition exists to prevent an alleged infringer from being sued multiple times under multiple patents by the same patentee when the patents claim the same subject-matter.

There are, however, situations in which multiple patents may be granted to the same person which overlap in scope. For example, it is common practice for an applicant to seek a narrow scope of protection for a particular embodiment of an invention in order to try to get a patent granted quickly while seeking, at the same time, broader protection for the invention in a separate application (e.g. a divisional application). The reason for allowing this is that the EPO (alongside patent offices of the Contracting States) accepts that the applicant has a ‘legitimate interest’ in obtaining narrow protection quickly while being able to subsequently obtain the broadest protection to which they are entitled (which may take many years).

In the decision under appeal in T0318/14, Nestec S.A. had argued that there is a comparable legitimate interest in obtaining two separate European patents where one claims priority from the other (typically referred to as ‘internal priority’), even when the subject-matter claimed in the applications is identical. The reason is that the patents will have different filing dates and so expire at different times (the later priority-claiming application expiring up to one year later than the earlier application from which priority is claimed). The priority-claiming patent application can therefore confer a potentially valuable extended duration of patent protection.

Nestec argued that previous Enlarged Board of Appeal Decisions which addressed double patenting only addressed double patenting in the context of divisional applications (which share the same filing date and so would expire at the same time as each other or the parent application from which they are derived) and so do not provide justification for refusal.

The Examining Division of the EPO disagreed and refused a second priority-claiming application on the grounds that, although the established case law is based on a conflict arising in connection with divisional applications, no positive conclusion had been drawn in the earlier decisions in connection with double patenting arising between a first European patent application and a second European patent application which claims priority from the first application.

The decision of the Examining Division is now under appeal. The Board has acknowledged that there is an unresolved issue and so has referred several questions to the Enlarged Board of Appeal, specifically with the intention of trying to clarify when the EPO may refuse a patent and whether any distinction can be drawn between applications which have the same actual filing date (e.g. divisional applications) and applications which do not (e.g. a European application which claims priority from another European application).

The answers from the Enlarged Board of Appeal could have a significant impact on patent filing strategies before the EPO. If the answers provided by the Enlarged Board of Appeal support the Decision then applicants will need to consider carefully the circumstances in which a priority filing application should be prosecuted through to grant in favour of a later priority-claiming application.