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UK: US and EPO post grant practice compared

The America Invents Act (AIA) of 2011 introduced a number of changes to the US patent system, including significantly increasing the options available for challenging the validity of a granted patent. Among these options it is the process of post grant review, a trial proceeding at the new Patent Trial and Appeal Board, which holds the most in common with opposition before the European Patent Office.

For the validity of a patent to be challenged in post grant review, it is essential that the patent was issued from an application subject to the first to file provisions of the AIA. If this criterion is satisfied then a request for post grant review may be validly filed, as in Europe, within nine months of patent grant.

It is also the case that a post grant review may be validly filed within nine months of grant of a reissue patent. Grant of a reissue patent is sought to correct an error in the originally granted patent, and may result in a broadening of the scope of the claims granted in the first instance. In contrast to this, under Article 105a, post grant amendment of a European patent must only limit the scope of the claims. In light of these differences, the ability to challenge the validity of a reissued US patent, unavailable in Europe after Article 105a amendments, may be clearly understood.

In both the US and Europe, any person who is not the patent owner may challenge the validity of a granted patent, although the filing of a post grant review comes with the additional caveat that the person has not previously filed a civil action challenging validity. In addition to this similarity, the grounds available for the validity challenge in the US (novelty, obviousness, written description, enablement and indefiniteness) are broadly equivalent to those available for a European opposition (novelty, inventive step, patentable subject matter, insufficiency and added subject matter).

The comparable nature of post grant review and opposition further extend into the appeals process. At the conclusion of a European opposition, the decision reached may be appealed by any party adversely affected, arguably narrower than the US standard for appeal where the party must only be dissatisfied with the decision.

Finally, practice in the US does significantly diverge from that in Europe in any subsequent infringement proceedings. In the US, post grant review creates estoppel which prevents grounds raised during post grant review being raised again during subsequent infringement proceedings. In Europe this is not the case, as any subsequent infringement proceedings would be before a national court (although future cases may, once it is established, be heard before the Unified Patent Court). As such, the issues raised during opposition may be raised again during infringement proceedings, depending on national law.

In summary, the US process of post grant review shares many similarities with European opposition. However, the processes are not identical, with one of the most significant differences being the estoppel created by post grant review. Consideration of this difference between the processes must form a key pillar of any advice presented to clients on this issue, especially where there is the potential for future infringement proceedings.


Helga Chapman 

Chapman + Co18 Staple GardensWinchester SO23 8SRUnited KingdomTel: +44 1962 600 500

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