1 August 2017
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In many jurisdictions a product or process may be held to infringe even though it falls outside the literal wording of a claim, if it is considered to be equivalent to the claimed invention. This is known as the “doctrine of equivalents”.

In the UK, the scope of protection of a claim is historically determined by “purposive construction”, where the language of the claim is interpreted in light of the description and drawings. There is no explicit rule or precedent for considering equivalents.

However, in July 2017 the United Kingdom Supreme Court (UKSC) handed down its judgement in the case of Actavis UK Limited and others v Eli Lilly and Company. As a result of this judgement, the scope of protection afforded by a UK patent may not be limited to the literal meaning of the claims. In particular, the Supreme Court reformulated the well-known “Improver Questions” to help courts decide on patent infringement where equivalent features are to be considered.

Going forward, UK courts must ask the following questions in order to determine infringement:

  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 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?
  3. 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 light of these reformulated questions, it seems that the UK now has a doctrine of equivalents to help courts decide on claim scope and patent infringement. This will mean that the UK is now more patentee-friendly, when it comes to assessing infringement.

Other major jurisdictions already use some form of doctrine of equivalents. Here we look at how these compare to the new UK approach.


In Japan, the “Ball Spline Bearing” case of 1998 confirmed that products or processes which do not infringe the literal wording of a claim can nevertheless infringe if it is found to be equivalent. That case set out five requirements for infringement to be found in such a case. Briefly, these are:

  1. The part replaced should not be an essential part of the invention;
  2. Replacement of that part should achieve the object of the claimed invention and produce the same result as the claimed invention;
  3. Replacement of that part would have been obvious to a skilled person at the time of making the defendant’s product;
  4. The defendant’s product was not novel and non-obvious at the time of filing the patent application;
  5. There is no proof showing that the applicant intentionally excluded the defendant’s product from the claimed invention.

Earlier this year, the Supreme Court of Japan handed down a new decision considering the doctrine of equivalents, in the “Maxacalcitol” case. In that case, it was held that “an essential part of the invention” mentioned by the first requirement will be interpreted more broadly where the invention makes a large contribution to the art. In addition, the Court clarified that the fifth requirement was not met merely because a variant could easily have been conceived at the filing date of a patent but was not claimed. Instead, it has to be shown that the applicant had recognised that the variant could be used, yet intentionally had not included it in the claim.


The doctrine of equivalents has been a recognised part of U.S. patent law for a long time when compared to other jurisdictions. There are two tests which have been established by case law. A first test, the “insubstantial differences” test, considers whether the allegedly infringing product or process is substantially different from what has been patented. A second test, the three part “function/way/result” test, says that infringement occurs where the allegedly infringing product/process:

  1. Performs substantially the same function...
  2. ...in substantially the same way...
  3. ...to yield substantially the same result...
    ...as the claimed invention.

This year, the Court of Appeals for the Federal Circuit confirmed, in Mylan Institutional LLC v Aurobindo Pharma Ltd., that the “insubstantial differences” test may be better-suited in cases considered chemical patents.

Although this is a new, and potentially controversial, development in UK patent law, the doctrine of equivalents has been used in many other jurisdictions for a number of years. Whilst each jurisdiction applies its own test, the UK, Japan and the USA all require a variant to achieve the same result in the same way as a claimed invention for infringement to be found. It therefore seems that the changes in the UK further harmonise the rules of claim interpretation with these jurisdictions. When looked at from this perspective, the recent decision of the UKSC appears to be less controversial than some might think.

Ashley has experience in all stages of the patent application process, from drafting and prosecuting applications to grant for a wide range of clients in the engineering and electronics industries both in the UK and Europe. He also carries out Freedom to Operate (FTO) analysis and liaises with attorneys across other jurisdictions.

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