IP Insights: File wrapper estoppel

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In the context of the UPC, the file wrapper estoppel will become highly relevant, because some UPC member states do recognize the file wrapper estoppel in their legal systems. However, other member states, such as Germany, do not. Before we go into detail, Julia, could you explain what “file wrapper estoppel” means?

Under the doctrine of the file wrapper estoppel, statements made by the patentee vis-á-vis the patent office during prosecution are binding. It is noteworthy that in the end we are talking about “clear statements”, as the prosecution history is often rather vague.

However, in some instances, the applicant concedes to a narrow claim interpretation during prosecution proceedings in order to overcome objections of lack of novelty or inventive step. The file wrapper estoppel in these cases prevents the patentee from arguing a broader claim interpretation in subsequent infringement proceedings.

The file wrapper estoppel is also very important for cases which are argued under the doctrine of equivalents. If the applicant does not claim protection for certain embodiments so that such embodiments are not covered by the literal sense of the granted claims, it might be difficult in the light of such prosecution history to claim protection for these embodiments under the doctrine of equivalents.

But some terms may have a very specific meaning in the patent description. And the prosecution history can help to understand what exactly the patentee wanted to protect.

In German patent litigation, statements made by the patentee during prosecution are not binding for claim construction. They can only serve as a mere indication of how the person skilled in the art would understand a certain claim feature.

But there is one exception: Statements limiting the claim scope made during pending invalidity proceedings. Such statements are considered binding and thus limiting the claim scope if the parties in the invalidity and the infringement proceedings are identical.

What is also relevant for claim construction in Germany is the prior art mentioned in the description. A skilled person understands that the patented invention must distinguish itself from such prior art, as it cannot be assumed that the patentee wanted to patent such prior art. Therefore, prior art appreciated in the description is the starting point and one of the most important means of claim construction.