On 14 June 2016, the German Federal Court of Justice (X ZR 29/15 "Pemetrexed") confirmed prior decisions in which it held that patent infringement under the doctrine of equivalents can, in principle, not be assumed, if the patent discloses various ways that a certain technical result can be achieved, but only one of those possibilities has found its way into the claims.

The Court held that if the wording of the claims is narrower than what would have been necessary—considering the technical contribution of the patented invention to the prior art— competitors and other interested parties can rely on the applicant's carefully chosen words. The patent holder is not allowed to subsequently claim protection for something that he deliberately chose not to protect. According to the Court, this rule shall even apply when a person skilled in the art realizes that the effects of the invention go beyond the technical matter for which the applicant sought protection in the claims.

Also, embodiments that are not explicitly disclosed but that can easily be identified by a person skilled in the art from the specification are, in principle, excluded from equivalent patent protection. The latter, however, ultimately depends on the reader's perception of the patent document.

However, this principle, like every other in the field of IP law, has its limits. It shall only apply to circumstances where the patent document (explicitly or inherently) discloses more than one embodiment. An extension of this principle to embodiments that were available to a person skilled in the art only through a vague indication in the specification would, in the eyes of the Court, go too far because the availability of equivalent embodiments is a necessary precondition for a finding of infringement under the doctrine of equivalents. If these embodiments were also excluded from the scope of protection one would never be able to establish infringement by equivalence.

This article was originally published on AllAboutIP – Mayer Brown's  blog on relevant developments in the fields of intellectual property and unfair competition law. For intellectual property-themed videos, Mayer Brown has launched a dedicated channel available here.

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