Until recently, the question of infringement in UK patent law had been one of purposive construction of the claim. Whether the underlying invention was a lintel used in construction, a handheld epilator or a method for the production of a hormone, scope of protection would ultimately turn on ‘what the person skilled in the art would have understood the patentee to be using the language of the claim to mean.’[1] Although such an approach promised to deliver a simpler, more predictable assessment, it attracted heavy criticism for providing only limited protection against infringement by equivalent means. In order to be infringing, immaterial variants – that is, modifications with no significant effect on how the invention works – still had to fall within the language of the claim. Hence extending vertically could mean something other than a 90-degree angle, but a helical spring would never be a rubber rod in the eyes of the skilled reader. This limiting character of purposive construction led a commentator to define it as ‘contextual literalism’,[2] and many decried the UK approach as being inconsistent with the Article 69 Protocol to the European Patent Convention.
 
In Actavis v Eli Lilly, the UK Supreme Court parted ways with tradition to embrace a self-standing doctrine of equivalents. Following a doctrinal distinction between the issues of (1) interpretation of patent claims and (2) scope of protection, infringement now unfolds into a two-stage assessment which notionally suggests a closer alignment with other European jurisdictions. But what may be seen as a methodological shift to ensure compliance with international obligations – and a laudable harmonisation effort in itself – may bring about a more significant change to the law of infringement. This paper attempts to investigate the potential impact of the Supreme Court’s decision on patent policy and, in particular, the extent to which some of the normative propositions injected into this new equivalence regime are justified.
 

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