Using prosecution history in UK infringement proceedings

Using prosecution history in UK infringement proceedings

In the UK, prosecution history has rarely been considered during infringement proceedings. Lord Hoffman famously stated in Kirin v Amgen (2005) that “life was too short” to assess the prosecution history of a patent in view of what he believed to be the limited assistance it can provide when carrying out claim construction. But following recent Supreme Court developments, has the position changed in the UK?
It boils down to; whether when trying to decide what a claim means, the debate that took place while the patent was being granted, should be considered. Attitudes to this use of the prosecution vary between jurisdictions. When considering whether a product infringes a patent, the court first assesses the extent of protection afforded by the patent. In effect, the court interprets the claim feature by feature. Claim construction in this manner allows the court to determine whether the infringing article has all the features required by the claim.
In the US, the prosecution history with the USPTO is often used by the courts to aid in the interpretation of the claims. Concessions made by the patentee during prosecution can therefore sometimes be considered to limit the scope of equivalence that can be sought.
Recently, Actavis v Eli Lilly (2017) not only established a doctrine of equivalents in UK law, but also introduced a test for whether prosecution history should be considered during infringement proceedings. In Actavis Lord Neuberger took the view that the prosecution history should be used if one of two following conditions are met:

  1. The point at issue is unclear from the specification and claims and can be unambiguously resolved from the prosecution file, or

  2. ignoring the contents of the file would be contrary to the public interest.

Much has been written about how this might impact claim interpretation in future cases, less about how or whether attorneys should modify their behaviour during prosecutions to minimise risk. Writing in 2017 we considered this to be unlikely to require significant change to our day to day practice, given our awareness of the effect statements made in Europe could already have in US proceedings. However, we have been on a watching brief to see whether Lord Neuberger’s statements might open the door to a more US-style system, and at least one judge has stated a fairly strong position.

L’Oréal v RN Ventures (2018)

The UK High Court made a landslide decision in the case of L’Oréal v RV ventures, who had argued that that during prosecution L’Oréal had limited its main claim (to a mechanical device for the treatment of acne) to a tension/compression mode of action, and in doing so, excluded shear modes of action from infringing.
Henry Carr J flatly rejected this line of argumentation, finding that neither of the two conditions above were met. The issue at hand was not unclear in light of the specification and claims and the prosecution history did not unambiguously resolve any issue.
RN Ventures had argued that, as L’Oréal complied when the examiner required that the claims to a shear mode of action be deleted, this amounted to L’Oréal disclaiming the shear mode of action such that it would be contrary to the public interest for the contents of the file to be ignored. However, Carr J found that L’Oréal was not under any duty to correct misunderstanding on the part of the Examiner about the scope of the claims and that this did not amount to a clear disclaimer of the shear mode.
Carr concluded the section of his judgement on use of prosecution history by stating “reference to the prosecution history is the exception, and not the rule” and warning “parties should think carefully in future before incurring additional costs in arguing about it”.

Legal and practical implications

In summary, Actavis doesn’t appear to be having the impact on interpretation with respect to the use of prosecution history that some may have expected. From an attorney point of view, it looks like the best practices we outlined in 2017 continue to apply: treat the risk of US consequences as the higher priority. Evidently, explicit disclaimers should only be made with caution. Perhaps, when accepting an Examiner driven amendment it should be made clear that this is for purposes of furthering prosecution rather than as an expression of legal or technical agreement, but even this may be unnecessary in view of the Court’s clear steer. And, it is worth recalling that in Actavis Baron Neuberger actually reviewed the prosecution history in a broadening rather than narrowing manner, to the benefit of the patentee.
Both parties have been granted leave to appeal to the Court of Appeal, we will continue to watch the situation regarding L’Oréal v RN Ventures and the wider landscape surrounding the use of prosecution history in infringement proceedings. However, for now, it appears that no changes to every day practice are required.
To discuss this article in more detail or to raise any questions on the subject matter, please contact Gwilym or Sam, who would be delighted to hear from you.

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