A UK Doctrine of Equivalents?

     The UK Supreme Court recently decided (1) to modify the way patent claims should be interpreted for deciding on infringement.  In doing so, they appear to have harmonised the UK approach slightly more with that of other European countries and the USA.  Some commentators have also noted that the decision shifts the legal test slightly more in favour of patent owners.

     Different jurisdictions have taken different positions for interpreting claims, between slavishly applying the literal meaning of words at one extreme, and treating the claims merely as a guideline at the opposite extreme.  The traditional UK approach is considered to be closer to a word-based interpretation, and although the purpose, or function, of a claimed feature may be taken into account, the UK Courts have been reluctant to stray too far from the actual words used in a claim.  In addition, they have avoided referring to what the applicant said to the IP Office during the patent grant process, the ‘prosecution history’, in contrast to the US approach. 

     While the basic question applied by UK Courts has been: “what would the skilled person have understood the patentee to mean?”, the so-called ‘Improver’ questions have been used to decide whether a claim is infringed.  In Actavis v Lilly (2017), the Supreme Court held that a claim was infringed by a product comprising a chemical compound variant outside the literal scope of the claim, regarding the variant as being equivalent to the one claimed (i.e., pemetrexed disodium).  In doing so, the Court felt it necessary to modify the Improver questions to read as follows:

  1. Notwithstanding that it is not within the literal meaning of the relevant claim(s) of the patent, does the variant achieve substantially the same result in substantially the same way as the invention? i.e. the inventive concept revealed by the patent?
  2. Would it have been obvious to the person skilled in the art, reading the patent at the priority date, but knowing that the variant achieves substantially the same result as the invention, that is does so in substantially the same way as the invention?
  3. Would such a reader of the patent have concluded that the patentee nonetheless intended strict compliance with the literal meaning of the relevant claim(s) of the patent was an essential requirement of the invention?

     If the first two questions are answered “yes” and the third question is answered “no”, then the claim is infringed.

     The Court also appeared to open the door to taking the prosecution history file into account for interpreting the claims, in certain circumstances.  In particular, reference to the prosecution file may be appropriate where a) the claims, description and drawings were not sufficient to clarify an important point at issue, and the prosecution file would unambiguously resolve the point, or b) it would be contrary to the public interest to ignore the prosecution file.  However, the Court stated that a skeptical approach should be adopted towards using the prosecution history to interpret claims.

     While these modifications to assessing infringement in the UK may be rather small, and impact of this decision remains to be seen, greater international harmonization of the approach is surely welcome.

(1) Actavis UK Limited and others v Eli Lilly and Company ([2017] UKSC 48)