Prosecution History Estoppel in Europe?

The US Supreme Court’s decision in Festo Corporation v Shoketsu on 28th May 2002 has brought a degree of certainty to the status of the doctrine of equivalents in US law. The question of the extent to which Article 69 of the European Patent Convention and the associated Protocol on Interpretation embodies any doctrine of equivalents is considered elsewhere in this newsletter. The special limitation on that doctrine of file wrapper or prosecution history estoppel and its application in Europe will be considered here.

The Supreme Court specifically dealt with the issue of prosecution history estoppel in the Festo judgement and stated, “We agree with the Court of Appeal that a narrowing amendment made to satisfy any requirement of the Patent Act may give rise to estoppel”. The Court recognised that prosecution history estoppel may arise not only in respect of amendments which are necessary to overcome novelty and obviousness objections with respect to cited prior art but that any amendments which are filed in response to patentability objections could give rise thereto. Therefore, a clarifying amendment which narrows the scope of a claim, for example, could lead to estoppel.

Where claims are amended, "the inventor is deemed to concede that the patent does not extend as far as the original claim". In any action for infringement, the burden of proof falls on the patentee to show that at the time of amendment a skilled person could not reasonably have drafted a claim which would cover the equivalent against which the patent is being enforced. The patentee must establish that the equivalent was unforeseeable at the time the claim was drafted, the amendment did not surrender the particular equivalent in question or there was some reason why the patentee could not have recited the equivalent in the claim.

During the November 2000 Diplomatic Conference to amend the European Patent Convention, the issue of prosecution history estoppel was considered. Originally, there was a proposal to include a provision in Article 69 and the associated Protocol on Interpretation (which governs national courts’ interpretation of patents) which would implement a form of prosecution history estoppel in European law. This particular proposal was not agreed to, though a proposal to expand the Protocol to encompass equivalents has been agreed (see “The Protocol Questions” above).

 

File history evidence can be used in claim interpretation

A European patent is always enforced in the national courts and therefore any parallels to the US practice of prosecution history estoppel are to be found at the national level. Certain European national jurisdictions have adopted approaches which allow the courts to consider extraneous evidence when interpreting the claims (Ciba-Geigy v. Oté Optics, Dutch Supreme Court, 13 January 1999), and now in the UK case of Rohm & Haas v. Collag [2002] FSR 28, the Court of Appeal referred to a letter filed by the patentee during prosecution to clarify the meaning of a claim. Lord Justice Walker stated that a letter from the patentee submitted during prosecution “could be of assistance in resolving some puzzling features of the specification.”

Although a far cry from estoppel per se, it appears that the English Court of Appeal is prepared to consider extraneous evidence when issues of construction cannot be determined solely in reliance on the content of the patent itself.

 

Comment

Every practitioner must be wary of the doctrine of prosecution history estoppel, not merely because a foreign jurisdiction might consider evidence from a file history, but because we cannot predict the circumstances in which the file history may some day influence the Court.

Is it unfair to permit a patentee to argue for a certain claim construction during prosecution and then ignore that when it comes to infringement proceedings? Might this allow the patentee to have his cake and eat it?

The rationale behind not allowing extrinsic evidence to be introduced when construing a patent, like the rationale behind not allowing parliamentary speeches to be considered when interpreting legislation and like the rationale behind interpreting a contract from within the four corners of the document, is that the introduction of extrinsic evidence opens up the task from a manageable question of law for the Court to an open-ended question of fact with all the associated uncertainties that follow. But the body of evidence to be considered is not open-ended. It is at least limited to the prosecution file. Indeed, it usually consists of just a handful of letters and a few prior art documents. In an era which sees calls for less rigid interpretation of claims, industry cries out for certainty as to how claims are to be interpreted. A natural source of guidance is the file history. Indeed, in the United States where courts have no choice but to apply a doctrine of equivalents, the file history is the first place to look for guidance.

Permitting the defendant to refer to the file history would require the Court that considers infringement to also look at how the invention is distinguished over the prior art. That is standard practice in Courts of the United Kingdom, but Courts elsewhere in Europe may be reluctant to go down that path.