Patents and Equivalents – A comparative study of the doctrine of equivalence in Anglo-American and Nordic patent laws
Master’s thesis by Miko Leach (available and accessible on Edilex and Helda) was awarded in 2020 by Finnish Association for Industrial Property Rights.
Recent reforms in certain European patent laws have sparked discussion about equivalents and the doctrine of equivalence. This area of patent law has remained largely outside the scope of legislative harmonisation, given that the doctrine of equivalence is understood as part of the law of patent infringement, which is subject to the competence of national patent laws.  This thesis studies comparatively how the doctrine of equivalence works in four different patent laws, namely American, English, Swedish and Finnish patent laws. Two of these are representative of common-law systems and two are representative of Nordic civil-law systems. Each country except the U.S. participate in the European Patent Convention (“EPC”), which has enabled the harmonisation of several aspects of patent law within the jurisdiction of the EPC, with the notable exception of the law of patent infringement.
In the EPC, the source of equivalents is Article 2 of the Protocol on the interpretation of Article 69 EPC. It provides that equivalents must be taken into account when interpreting the scope of protection of patents, which pursuant to Article 69 EPC (and respective provisions in the national patent laws of the participating member states) is defined by interpreting the patent claims (i.e. claim construction). Patent infringement relies in part on claim construction. If any third-party device (e.g. product or method) falls in the scope of protection of the patent, certain acts taken by the third party in relation to the device are likely to lead to the infringement of the patent, which (provided that the patent is not invalidated or the case is not settled) entitles the patentee to certain remedies including injunctions, compensation and damages.
Whether or not any third party infringes the patent depends on the scope of protection of the patent. If the patent claims are construed more literally, the allegedly infringing device by and large must contain features identical with the patent claims. On the other hand, the effect of the doctrine of equivalence is to include technically similar replacements or variations in the scope of protection of the patent. This means that the patent claims are construed beyond their literal wording, which results in a scope of protection extending to a certain range of equivalents that can be said to form part of the patent monopoly. The extent to which courts are willing to depart from the literal wording of the patent claims varies, whereby this thesis explores how the doctrine of equivalence is approached in the given four patent laws. The objective is to gain a more systematic understanding on the doctrine of equivalence.
This study is approached through four comparative questions, which target different aspects of the doctrine of equivalence:
- When does the doctrine of equivalence apply and how is it applied – what is the legal test for determining infringement under the doctrine of equivalence, and what are the factual and legal prerequisites for the application of the doctrine of equivalence?
- On what basis is account taken of equivalents in proceedings concerning patent infringement? What past and present considerations have given effect to taking account of equivalents in the first place?
- How, if at all, has the scope of application of the doctrine of equivalence been limited? In other words, are there predetermined grounds for exclusion of the doctrine of equivalence? Furthermore, is there a certain type of patent that is more likely to benefit from the added scope of protection outside the literal construction of patent claims than a certain other type of patent?
- What types of defences are available to the defendant, which allegedly has infringed a patent under the doctrine of equivalence?
The observed similarities and differences are then analysed through comparative law, which helps understand how the globalisation of law and legal pluralism, amongst other phenomena of comparative law, affect the formation of similar or different approaches to the doctrine of equivalence.
Without going into great depth, the thesis concludes that American, English and Swedish patent laws have given effect to the doctrine of equivalence in the form of a patent infringement test, whereas in Finland the doctrine of equivalence seems to operate at the level of claim construction. The difference this makes is that claim construction is a matter of law, whereas patent infringement also depends on a factual matrix. The prerequisite or preference for the application of the doctrine of equivalence seems to be pioneering inventions, which given their remoteness from prior art in terms of novelty and inventive step seem to justify departing from the literal meaning of the patent claims. American and Swedish patent laws have clear metes and bounds on the application and limitation of the doctrine of equivalence, and American patent law has a sophisticated defence specific to the doctrine of equivalence: ensnarement. This defence seems to be reflected in English and Swedish patent laws in the Formstein defence. In Finland, the doctrine of equivalence exists as a clear patent infringement test only in legal literature,  whereas this test does not seem have been applied in practice, even though after the publication of Norrgård’s book there have been certain legal proceedings invoking patent infringement under the doctrine of equivalence. In English patent law, the boundaries of the doctrine of equivalence seem to still be developing given the very recent reform in the English approach to the doctrine of equivalence.
The similarities and differences are explained through various phenomena of comparative law. For the similarities, legal globalisation is particularly interesting. For example, dialogue between judges plays a significant role in legal harmonisation outside the scope of legislation. In Actavis v Eli Lilly, Lord Neuberger noted, “[…] it is sensible for national courts at least to learn from each other and to seek to move towards, rather than away from, each other’s approaches […]”  (Emphasis added) On the other hand, legal pluralism helps understand the differences. For example, the weight given to certain patent law theories on claim construction, such as the central and peripheral theories, as well as the patent bargain theory, seems to affect the scope afforded to the doctrine of equivalence. In addition, differences that had been anticipated due to the overall differences between common law and civil law proved insignificant in this area of law. In fact, it appeared that American and Swedish patent laws have had similar approaches the doctrine of equivalence even before the doctrine of equivalence was established in English patent law.
The comparison of the different approaches and analysis through comparative law incidentally leads to questions about the justification for the doctrine of equivalence and whether a separate patent infringement test is necessary. In the American landmark judgment in Graver Tank, Justice Jackson opined something fundamental about the doctrine of equivalence: limiting the patentee to the literal meaning of the claims would convert the protection of a patent into a hollow and useless thing.  (Emphasis added) In other words, the integrity of the patent law system must not be compromised by allowing third parties to avoid the scope of protection of the patent by making insignificant variations to the invention disclosed and protected by the patent. The doctrine of equivalence safeguards not only investments in inventiveness but also the reliance and expectations of patentees in the integrity of the patent system. It is challenging to conclude whether the correct approach to the doctrine of equivalence is a separate patent infringement test or whether it is sufficient to give effect to the doctrine of equivalence solely as part of claim construction. However, in Actavis v Eli Lilly, Lord Neuberger found that the lack of a separate patent infringement test for the doctrine of equivalence led to the conflation of issues of claim construction and patent infringement, which in my opinion seems a perfectly reasoned justification for approaching the doctrine of equivalence through a separate patent infringement test.
 In the European patent system, Article 64(3) EPC provides that patent infringement is a matter of national patent law. While claim construction may be harmonised, the exclusive competence of national courts in patent infringement means that differences due to lack of legislative harmonisation are prone to occur.
 See Norrgård M, Patentin loukkaus (WSOYpro 2009).
 Actavis UK Ltd v Eli Lilly & Co UK Ltd & Ors  UKSC 48,  (Lord Neuberger).
 Graver Tank & Mfg. Co. Inc. v. Linde Air Products Co., 339 U.S. 605, 607 (1950).