In one of the most important judgments from the UK courts for many years, the Supreme Court has fundamentally changed how the scope of protection conferred by a patent is assessed in the UK.
Previously, the extent of protection was assessed in a single step using "purposive construction", in which the skilled person assessed what the person skilled in the art would have understood the patentee to be using the language of the claim to mean.
The new approach requires a two-stage test:
(i) does the variant infringe any of the claims as a matter of normal interpretation; and, if not,
(ii) does the variant nonetheless infringe because it varies from the invention in a way or ways which is or are immaterial? If the answer to either issue is "yes", there is an infringement; otherwise, there is not.
The first stage will involve familiar issues of claim interpretation. The second stage of the test introduces a "doctrine of equivalents" into UK law. Whether-or-not an alleged infringement which does not fall within the scope of the claims using normal interpretation still infringes as an "equivalent" will be assessed by reference to the facts of the case and expert evidence. The issue will generally be answered using a reformulation of the "Improver questions":
(i) 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, ie the inventive concept revealed by the patent?
(ii) Would it be 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 it does so in substantially the same way as the invention?
(iii) Would such a reader of the patent have concluded that the patentee nonetheless intended that strict compliance with the literal meaning of the relevant claim(s) of the patent was an essential requirement of the invention?
In order to establish infringement in a case where there is no literal infringement, a patentee would have to establish that the answer to the first two questions was "yes" and that the answer to the third question was "no".
As noted in the judgement by Lord Neuberger, this different approach may lead to a different conclusion on infringement than would have resulted from using the previous one-stage approach: "I have considerable difficulties with the notion that there is a single conflated, or compound, issue, and, even if that notion is correct, that that issue raises a question of interpretation. Indeed, in my view, to characterise the issue as a single question of interpretation is wrong in principle, and unsurprisingly, therefore, can lead to error." Consequently, it is worth reconsidering infringement opinions that were prepared under the old law.
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