Doctrine of equivalents in patent law: comparative approaches and key case law

The doctrine of equivalents occupies a central place in patent law, as it aims to protect the’essence of the patented invention by sanctioning infringement even when it does not literally adopt all of the claimed characteristics. Faced with the ingenuity of third parties seeking to circumvent the wording of the patent, this doctrine offers a legal response that goes beyond a mere literal analysis of the claims.

This article proposes a comparative study approaches developed in several legal systems (France, Germany, the United Kingdom, and the United States), highlighting major case law references.

I. Foundations and stakes of the doctrine of equivalents

1 – General definition

The doctrine of equivalents can be summarised as the possibility for a patent holder to sue for infringement a third party who, without exactly reproducing the claimed elements, uses means of technically equivalent producing the same function and the same result that the invention. This doctrine protects the «inventive substance» against minor or purely formal modifications.

2 – Practical considerations

• Balance between legal protection and security By broadening protection beyond the wording, the scope of the patent is strengthened, but there is a risk of adding uncertainty for market players.
• Fighting literal circumvention Without the doctrine of equivalents, a mere cosmetic or marginal change could nullify the protection conferred by the patent.

II. The doctrine of equivalents in French law

1 – Texts and principles

In France, the Intellectual Property Code (IPC) does not explicitly mention the doctrine of equivalents, but the’Article L. 613-3 of the CPI It prohibits counterfeiting when there is Usage unauthorised use of the patented invention. Case law has refined the notion.

2 – Jurisprudential development

• Wire wool stop« (Cass. com. 20 December 1961): The Court of Cassation recognised the possibility of infringement being established by reason of’equivalence For a summary of the case law see here).
• Criteria applied French case law examines the function and the result obtained by the substituted means. If the’person skilled in the art recognises that the element in question performs the same function and achieves the same technical result, infringement may be established.
• Essential or secondary character It is therefore necessary to determine whether the modified element is essential to the invention and plays a role; if the modification concerns an accessory aspect, equivalence applies more readily.

3 - Precautions

French courts ensure that patents are not given excessive scope, so as not to encroach upon the Legal certainty third parties and to respect the principle of specialty the scope must remain confined to the claimsArt. 69 EPC and Interpretation Protocol).

III. The German approach: the triple condition

1 – Legal basis

Dans le grand ouest, en Allemagne, le doctrine of equivalents also stems from case law, in connection with the Patent Protection Act (Patents Act). The courts, particularly the Federal Court of Justice (BGH), have developed a Three-part test.

2 – German three-part test

• Same effect The contested solution must produce essentially the same technical effect as that described in the claims.
• Obvious character For the professional, the substitution should appear as an obvious solution to achieve the same result.
• Same inventive step the variant must not depart from the initial inventive step. If the substitution provides a new inventive effect, it escapes equivalence.

3 – Notable case law

• Judgment «Formstein» (BGH, 1986) the Formstein defence allows the defendant to argue that the equivalent variant falls within the prior art or is obvious, which would invalidate the claim if it were to include this variant.
• Judgment «Schneidmesser I» (BGH, 2002) The Court recalled the need to verify the tradesman's awareness of the obvious substitution.

IV. The British Approach: Extension via Actavis v Eli Lilly

1 – Historical evolution

Traditionnellement, le Royaume-Uni adoptait une approche où la conformité était le fer de lance de sa stratégie de mise sur le marché pour les produits d'intérim et à faible risque. “purposive interpretation” (Teleological interpretation), sometimes rejecting the American approach of equivalence.

Catnic Components Ltd v. Hill & Smith Ltd (HL, 1982) the House of Lords proposed a combined test of fair protection for the invention and reasonable certainty for third parties.

2 – Actavis UK Ltd v. Eli Lilly and Company (2017)

• Reversal the Supreme Court has introduced a test in three questions resembling a doctrine of equivalents:
  1. Does the variant achieve Substantially The same result in the same way?
  2. Would a person skilled in the art have understood, as of the priority date, that this variant achieves the same result?
  3. Is the variant clearly excluded by the wording of the claim?
• Henceforth, a solution can fall under counterfeiting even if it does not reproduce in the strict sense the words of the claim, if equivalence is established.

3 – Consequences

The United Kingdom is drawing significantly closer to Germany, adopting a broader concept of protection by equivalents. Subsequent rulings (e.g. Icescape Ltd v. Ice-World International BV, 2018) confirm this new direction.

V. The United States: «Function-Way-Result» and the limits of estoppel

1 – Historical Foundations

• The American doctrine of equivalents dates back to Graver Tank & Mfg. Co. v. Linde Air Products Co.(1950), where the Supreme Court introduced the “function-way-result” test.
• This test assesses whether the infringing invention exercises the same function, of The same way, to arrive at the same result that the patented invention.

2 – Limitations: Prosecution History Estoppel

• Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co. (2002) The Supreme Court has refined the rule of estoppel. If the patent holder has narrowed their claims during examination (to obtain grant), they can no longer invoke equivalence on the abandoned or amended part.
• Estoppel serves as a balance to preserve predictability: one cannot retroactively claim equivalent protection on a point that one has explicitly abandoned opposite the Patents Office.

3 – Scope

Despite estoppel, the doctrine of equivalents remains very much present. US courts often distinguish literal infringement and infringement under the doctrine of equivalents, in order to cover a broad protection for validly drafted patents.

VI. Convergence and Divergence: A Comparative Overview

Convergence :

• All systems (France, Germany, United Kingdom, United States) recognise the need to widen protection to prevent abusive circumventions.
• The concepts of same function/result and of’evidence for the connoisseur are found in each jurisdiction, in various forms.

Divergences :

• France balance through the Function-result and the analysis of whether or not the substituted element is essential.
• Germany Test en three sections, completed by the Formstein defence.
• United Kingdom post-Actavis, adoption of a Triple test likened more to the German equivalent.
• United States test “function-way-result”, limited by the prosecution history estoppel.

Effect of the Interpretation Protocol to Article 69 EPC :

Article 69 of the European Patent Convention (EPC) and its Protocol advocate for a middle ground between literal and extensive interpretation. European countries follow this logic, to varying degrees.

Conclusion

The doctrine of equivalents is established in most patent regimes as an essential instrument for ensuring the effective protection of the invention. In France, l’accent est mis sur la function and the result, en Germany, the triple condition (même effet, évidence, valeur inventive), au United Kingdom, le test Actavis, et aux United States, l’approche “function–way–result” modulée par le prosecution history estoppel. La tendance générale est à la convergence, chaque pays cherchant à préserver la sécurité juridique tout en évitant une lecture trop restrictive des revendications. La jurisprudence récente (Actavis v. Eli Lilly au Royaume-Uni ou Festo aux États-Unis) confirme l’importance croissante de l’équilibre entre l’étendue de la protection et la prévisibilité pour les tiers. En pratique, l’person skilled in the art demeure la figure centrale de l’analyse, et la recherche d’une solution technique équivalente reste le pivot pour déterminer la contrefaçon par équivalence. Ainsi, la doctrine des équivalents, si elle s’applique avec prudence, constitue un rempart efficace contre les contournements littéraux, tout en ménageant la Legal certainty nécessaire au fonctionnement du marché.