A Step Towards File Wrapper Estoppel in the UK

Author:Mr Gareth Morgan
Profession:Herbert Smith

Earlier this week, the Court of Appeal gave judgement in a patent action between Rohm & Haas and Collag. The action turned on the meaning of "surfactant" in the claims. The expert evidence was that surfactant could have at least two meanings and it was not clear from the specification which of these meanings the patentee had intended. However, some guidance on the intended meaning of the word could be gleaned from a letter that the patentee had written to the EPO during the course of prosecution. Was this letter admissible evidence?

The Court of Appeal started from the position that there was no English authority on the admissibility of statements made by the patentee during the course of prosecution. However, the Dutch approach is to take account of such statements, but only where the meaning of the claims would not have been clear to the skilled reader. The Court of Appeal endorsed this approach, but cautioned that such statements would not have the same weight as published prior art.

This is an interesting judgement because it is the first time that the English Courts have considered the...

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