European Patent Prosecution: Added Subject-Matter Pitfalls to Avoid

European Patent Prosecution: Added Subject-Matter Pitfalls to Avoid

We frequently handle European and UK patent applications on behalf of clients based outside Europe. Clients (and their attorneys) are often very familiar with patent law in their own countries, but not always as familiar with European patent law. For the most part, patent law is fairly well harmonised across the world, but there are still some areas where law and practice can differ quite a lot.

Added subject-matter

Some of the most gnarly problems we wrestle with in such applications relate to added subject-matter. Broadly, this is the extent to which a patent application can be amended during prosecution (typically to overcome prior art disclosures identified in searches, or to address an objection that the claims are unclear). 

In Europe (and the UK), the legal test is that any amendments to a patent application must not extend the subject-matter of the application beyond the content of the patent application as filed. Case law has defined this fairly strictly. The subject-matter for any amended claims must be directly and unambiguously derivable from the application as filed. The ambiguity point is key to understanding how this operates in practice. 

Let’s say that the original independent claim is directed to “A widget comprising a fastener formed from metal”. The detailed description includes a first example of the widget having a screw fastener formed from brass and having a cylindrical handle. A second example in the detailed description describes a widget having a nail formed from steel and having a grip surface to hold the widget. Clearly, both examples are within the scope of the original independent claim.

In the claim, there are several sources of potential ambiguity. The type of the fastener is not specified (it might cover rivets, screws, nails and others). The material of the fastener is specified only as metal, but not a specific metal. The widget may comprise only the fastener without any handle or grip surface, or it may comprise the fastener and the cylindrical handle with a grip surface, or it may comprise the fastener and the cylindrical handle but without a grip surface.

As a general rule, claim amendments in Europe are only permissible where they do not introduce or resolve an ambiguity that was not already present or resolved in the application as filed.

In the present example, the independent claim could be amended to specify all of the features from one of the examples, but could not necessarily be amended to specify that the widget comprises a cylindrical handle without also specifying that the fastener was formed from brass. This is because the only disclosure in the application as filed of a widget having a cylindrical handle also had a fastener formed from brass. As a result, specifying that the widget comprises a cylindrical handle and a fastener formed from metal introduces an ambiguity (as to the material of the fastener in widgets comprising cylindrical handles) that was not present in the application as filed.

This strict implementation of the rules of added subject-matter can cause difficulties when seeking to pursue amendments used successfully elsewhere (such as to secure grant of a US patent).

Sometimes, the amendment is still available, but requires a more detailed and involved argument to be submitted, or may entail multiple rounds of correspondence with the examiner, thereby increasing the costs of prosecution. In other instances, a desired amendment is just not possible, forcing an applicant to find another amendment which may not provide a scope of protection which is as commercially useful as might be hoped.

Another issue of particular relevance is what happens when an amendment is deemed, after grant of the patent, to have been impermissible. In Europe and the UK, added subject-matter is a ground of invalidity of a patent, which can be raised during European Opposition proceedings or revocation proceedings in several countries. Where the amendment is broader than a claim scope for which there is proper basis in the application as filed, the additional limitation can generally be introduced to rescue the claim and overcome the added subject-matter objection, thereby saving the patent from revocation on this ground.

However, where the amendment introduced a feature for which there was no basis, even in combination with other features, once the patent has been allowed to grant, and if there is no way to remove the added subject matter without in some way broadening the claims, no options are available to save the patent and it may be revoked in its entirety. This is obviously a worrying prospect.

What’s the solution?

Generally, we recommend that added subject-matter provisions in Europe are considered at the drafting stage. One particularly effective approach is to consider all potential amendments that might be desired during prosecution, and to make sure that suitable wording can be found in the application without relying on the detailed description. 

We offer a service where we review the claim set to file in first filings and to propose any additional text to be included in the patent application to reduce the chance that potentially desired amendments are unavailable in Europe (or other countries with strict added subject-matter requirements).

In any case, objections to European and UK patent applications during prosecution should be considered carefully, particularly where these are more complicated than simply inserting a feature from a dependent claim into an independent claim.

Author: Chris Cottingham. If you have any questions about this article or any other aspect of European patent prosecution, please do not hesitate to contact us.

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