The Supreme Court Rules on Patent Infringement and Claim Construction

25 July 2017

On 12th July 2017, in Actavis v Eli Lilly the UK Supreme Court issued a landmark judgment, clarifying the scope of what may be considered patent infringement; and clarifying the circumstances in which reference to the patent prosecution file may be used to assist the Courts.  The written judgement of the case in question can be read here.


Determination of Infringement by “Equivalents”

Interpretation of the scope of a patent claim, and deciding whether a product/process/use infringes a claim, can be difficult. Understanding the plain language of a patent claim can be difficult – and the scope given to a patent claim extends beyond its plain language. Assessing the extent to which a claim extends beyond its plain language is particularly challenging.

In assessing patent scope, over a 35-year course the UK has moved from:-
A position where “textual infringement” was considered separately from “infringement of the ‘pith and marrow’ [the essential core] of the invention”;
A period of “purposive construction” where the view of the skilled person reading the patent was taken into consideration in determining whether strict compliance with claim language was necessary (i.e. interpreting the claim to mean more than its plain language);
An attempt to square this approach with European Patent Convention law by rebadging tests developed under purposive construction as “Protocol Questions”;
Reversion to “purposive construction” but acknowledging that the Protocol Questions were a useful guideline
and now, with this latest judgement:
Back to (nearly) the beginning.


Apparent new test for Patent Infringement following this judgement
  • Does the product/process/use concerned fall within the literal meaning of the claim (as interpreted from the position of a person skilled in the art, with reference to the description and the drawings) – if yes – there is infringement.
  • If the product/process/use concerned does not fall within the literal meaning of the claim, is it a variant that meets a three-step analysis (similar, but not identical to the previous “Protocol Questions”) – if yes – there is infringement by equivalence.
Simplified comparison with “Purposive Construction”

The old tests required assessment of whether the variant had any “material effect”, and if not, whether this lack of material effect was obvious at the date of publication; if there was no material effect and that was obvious, then there was infringement unless it was clear the patentee meant to restrict to the literal language used.

The new tests require assessment of whether the variant achieves “substantially the same result” as the invention and whether (if the skilled reader knew it achieved “substantially the same result”) it would have been obvious at the priority date of the patent that it does so in “substantially the same way” as the invention; if the variant achieves “substantially the same result” as the invention, in “substantially the same way”, and at the priority date this would have been obvious –  there is infringement unless it is clear the patentee meant to restrict to the literal language used.


These changes are complex, but may be exemplified by assuming a patent had a claim to “a dog balancing a ball on its nose” with the description indicating that the result was general amusement. Does “a cat balancing a ball on its nose” infringe?

The old test, would have looked to whether, at the time the patent was published, it would have been obvious to a person skilled in the art of trained pets that substituting a cat for a dog would have no material effect on ball balancing. In the light of the uncooperative nature of cats, it might not have been obvious that there would be no material effect, and so non-infringement might have been the outcome.

The new test appears to be whether, to a skilled person having read the patent at the priority date of the patent, with the imputed knowledge that a cat can balance a ball on its nose to general amusement, it would be obvious that this achieves substantially the same result (general amusement) in substantially the same way (balancing a ball on the nose of a pet).  Infringement would appear to be the outcome unless it was clear to the reader of the patent that strict compliance with the literal meaning of the claim was an essential requirement of the invention.

This judgement provides welcome protection against those who attempt to step round the language of the claims by taking the core idea of the invention without stepping into the literal language.

The decision also provides an incentive to patent applicants to provide greater explanation in patent descriptions of how things work, (rather than simply what works), as the “how” may expand the scope of protection considerably if general claim language is not possible.

However, the judgement is not without some negative consequences.

  • Even less can the public rely on the words of a claim (this was always dangerous anyway).
  • Clearance searching may be more difficult if “ways” set out in the description must be searched as well as the specific terms set out in the claims.

One outcome of the decision may be more agreement between the decisions of UK courts and the courts of other major EPC jurisdictions.  Whether this is achieved remains to be seen: but if/when the Unitary Patent Court comes into effect, it may provide further guidance as case law develops.


Determination of the effect of Prosecution History

A further outcome of the judgement is the guidance of the Supreme Court that reference to the file may be used to assist in interpretation in some cases. The Supreme Court gave the guidance that reference to the file would only be appropriate where:-

  1. the point at issue is truly unclear if one confines oneself to the specification and claims of the patent, and the contents of the file unambiguously resolve the point, or
  2. it would be contrary to the public interest for the contents of the file to be ignored.

The Supreme Court gave, as an example of (2), the case where the patentee had made it clear to the EPO that he was not seeking to contend that his patent, if granted, would extend its scope to the sort of variant which he now claims infringes.

This cautious approach to references to the file is welcomed.


Summary of the Effects of the Decision and Other Comments

The importance of a well drafted description is emphasised by this case. Statements of function of the various parts of a claimed product/process/use may enable a broader scope than for applications where no clue is given as to function or manner of operation.

Those who have had opinions of non-infringement under the old law may be advised to revisit them.

Businesses must continue to take care when working close to the patented matter of another party.

Resolving infringement questions has always been potentially tricky.  If you require advice on a particular matter, we are here to help. Contact us at

Latest news

We Are Moving

From 1st October 2018 our new address will be:


Read more

Contact us

020 7822 8888

5 Pemberton Row
London EC4A 3BA