Double Jeopardy And European Patents

A recent EPO decision has challenged the conventional exclusion on double patenting. Neil Thomson asks where the decision leaves EPO practice, and what impact it will have on proceedings in the UK.

"It is an accepted principle in most patent systems that two patents shall not be granted to the same applicant for one invention" (Guidelines for Examination at the EPO, C-IV, 6.4)".

Or is it? A recent Technical Board of Appeal of the European Patent Office (EPO) has considered whether there is any legal basis for the above practice and, for a specific set of facts, concluded that there is not.

Technical Board of Appeal Decision T587/98

In the case appealed, the applicant Komag Inc filed a European application EP 91115600.8, claim 1 of which related to, inter alia, a structure comprising three layers in addition to a substrate: namely, a first dielectric layer formed on said substrate, a magneto-optic (recording) layer formed on said dielectric layer and a second dielectric layer formed on said magneto-optic layer.

Subsequently, a divisional application EP 95100700.4, was filed, the main claim of which claimed at least two layers in addition to the substrate: namely a recording layer which may be an optical or a magneto-optical layer, and a dielectric layer which may be formed either on the recording layer or between it and the substrate.

Denoting the combination of substrate, first dielectric layer and recording layer as 'A' and the second dielectric layer as 'B', the parent effectively claimed 'A' with 'B', while the divisional claimed just 'A'(implicitly with or without 'B').

At first instance the Examining Division of the EPO refused the divisional application since, in their view, the claims conflicted with those of the parent application. The decision was based on the Guidelines for Examination which state:

C-IV, 6.4 "The Convention does not deal explicitly with the case of co-pending European applications of the same effective date. However, it is an accepted principle in most patent systems that two patents shall not be granted to the same applicant for one invention. It is permissible to allow an applicant to proceed with two applications having the same description where the claims are distinct in scope and directed to different inventions. However, in the rare case in which there are two or more European applications from the same applicant ... and the claims of those applications have the same priority date and relate to the same...