Broadly speaking, the prohibition of double patenting is meant to mean that two patents cannot be granted to the same applicant for one invention (in the same jurisdiction). At a closer look, there is a plurality of facets, layers and aspects, producing an exhilarating spectrum of double patenting.

Thus, double patenting may arise in three situations where European patent applications are filed by the same applicant:

• Europeans patent applications filed on the same day;
• divisional and parent patent applications; or
• an European patent application claiming priority in respect of another European patent application (internal priority).

However, commentators on European patent practice have never stopped to stress that the European Patent Convention (EPC) does not prohibit double patenting.

After clarifying and harmonising numerous aspects of European patent practice, the Enlarged Board of Appeal (EBoA) of the EPO now gets a gigantic chance to revisit double patenting.

After the Examining Division decided to refuse European patent application EP 10 718 590.2 in accordance with the applicable Guidelines for Examination at the EPO (Guidelines), G IV, 5.4 under Art. 97(2) EPC in conjunction with Art. 125 EPC, allowing subordinate application of principles of procedural law generally recognised in the contracting states of the EPC, the applicant appealed the decision and auxiliary requested, as occasionally done, that the responsible Board of Appeal (BoA) refers a pivotal question to the EBoA.

The BoA did not, as usually done, discard the idea of referring the question to the EBoA, but also helped to develop the applicant’s question into a two-tier question, and decided at the end of oral proceedings held on 07 February 2019 in appeal case T 318/14 to refer a detailed set of questions to the EBoA.

Answers to the BoA’s questions to the EBoA may modernise the approach of the EPO to doubling patenting.

What has happened?

In earlier leading decisions G 1/05 and G 1/06, both relating to divisional patent applications, the EBoA said in passing that the principle of the prohibition on double patenting is based on the notion that an applicant has no legitimate interest in proceedings leading to the grant of a second patent for the same subject-matter if the applicant already possesses one granted patent for that subject-matter. The Guidelines extrapolated therefrom that in case that two or more European applications from the same applicant designate the same state or states and the claims of those applications have the same filing date or priority date and relate to the same invention only one of the applications can be granted.

However, for the present European patent application EP 10 718 590.2 claiming the internal priority of, and claiming the same subject matter as, an earlier European patent application, the applicant has a clear legitimate interest, as it is the filing date and not the priority date that is the relevant date for calculating the 20-year term of a patent. Of course, it is common practise to file a European patent application establishing a priority date for a new invention, towards the end of one year after the priority date to file a PCT application claiming the priority in respect of the European patent application, and towards 31 months after the priority date to enter the regional phase of the PCT application before the EPO.

The BoA agreed with the applicant that there is no uniform practice and even conflicting case law, and referred the following questions to the EBoA:

1. Can a European patent application be refused under Art. 97(2) EPC if it claims the same subject-matter as a European patent granted to the same applicant which does not form part of the state of the art pursuant to Art. 54(2) and (3) EPC?

2.1 If the answer to the first question is yes, what are the conditions for such a refusal and are different conditions to be applied where the European patent application under examination was filed

a) on the same date as, or

b) as a European divisional application (Art. 76(1) EPC) in respect of, or

c) claiming the priority (Art. 88 EPC) in respect of a European patent application on the basis of which a European patent was granted to the same applicant?

2.2 In particular, in the latter case, does an applicant have a legitimate interest in the grant of the (subsequent) European patent application in view of the fact that the filing date and not the priority date is the relevant date for calculating the term of the European patent under Art. 63(1) EPC?

For answers to the questions raised in T 318 /14, the EBoA may have to probe the real intentions of the legislators by going back to the archives and interpreting the Traveaux Préparatoires, the draft documents and minutes produced when the EPC was conceived back in the early 1970s.

There will be plenty of fragments in need of attention, and plenty of leeway for interpretation. However, it will be worth the efforts.