The Plant-e v. Arkyne Test for Assessing Equivalence

The validation of the Plant-e-Test by a German Local Division paves the way for the standardization of equivalence rulings at the UPC.

In Wonderland v. Cybex, concerning the infringement of patents relating to child seats and strollers (UPC_CFI_807/2024 and UPC_CFI_334/2025, decision of 27 May 2026), the Local Division (LD) Düsseldorf confirmed that the test for assessing equivalent infringement developed by the LD The Hague (UPC_CFI_239/2023, decision of 22 November 2024, para. 88 – Plant-e v. Arkyne) forms a coherent whole and is as such suitable for the examination of equivalence (Headnote 1).

This makes Wonderland v. Cybex one of the first UPC decisions to examine equivalence on the merits – and the first in which a German Local Division applies the largely Dutch-inspired Plant-e framework rather than the competing German Schneidmesser approach. The position of the Plant-e test as the emerging UPC standard has thereby been strengthened considerably, although the Court of Appeal (CoA) has yet to rule on the issue.

Competing approaches to equivalence

The Plant-e test consists of four questions: (1) Technical equivalence – does the variation solve (essentially) the same problem as the patented invention and perform (essentially) the same function? (2) Fair protection – is extending protection to the equivalent proportionate to a fair protection for the patentee, in view of his contribution to the art and of whether it is obvious to the skilled person from the patent how to apply the equivalent element (at the time of infringement)? (3) Reasonable legal certainty for third parties – does the skilled person understand from the patent that the scope of the invention is broader than what is claimed literally? (4) Is the allegedly infringing product novel and inventive over the prior art?

The German Schneidmesser test (BGH, decision of 12 March 2002, X ZR 168/00 – Schneidmesser I) asks: (1) Equal effect – do the modified means objectively perform essentially the same function as the claimed feature? (2) Findability – was the skilled person able, at the priority date and without inventive considerations, to identify the modified means as performing that function? (3) Orientation along the patent claim – are the skilled person’s considerations oriented along the claim such that the modified means are regarded as an equivalent solution within the meaning of the patent? A fourth question, sometimes treated as part of the canon, asks whether the description discloses the modified means but ultimately excludes them, whether by omission from the claim or by outright rejection.

Where the two tests actually diverge

The decision contrasts the “holistic” Dutch approach with the “legal-technical” German approach. In practical terms, this shorthand translates into three concrete differences:

First, the reference date.

Under Schneidmesser, the modified means must have been findable at the priority date; under Plant-e, it suffices that applying the equivalent element was obvious at the time of infringement. Post-priority technical knowledge can therefore support equivalence under the Dutch test but not under the German one – structurally, Plant-e is the broader standard, and this difference alone can be outcome-determinative, particularly for older patents in fast-moving fields.

Second, the yardstick: claim primacy versus fairness balancing.

The decisive third Schneidmesser question ties equivalence strictly to the patent claim: even a technically equivalent, readily findable variant falls outside the scope of protection where the claim wording reflects a deliberate narrowing choice by the patentee. Plant-e has no such claim-orientation filter; it instead balances fair protection for the patentee against legal certainty for third parties. Put pointedly: in borderline cases the German test asks what the claim permits, the Dutch test asks what result is fair.

Third, the role of the prior art.

Plant-e integrates the novelty and inventiveness of the attacked embodiment over the prior art directly into the test (question 4). In German practice, this corresponds to the separate Formstein defence, which must be raised by the defendant and is not part of the equivalence test itself – with corresponding consequences for the structure and burden of the parties’ pleadings.

The German clarification

On technical equivalence, the LD Düsseldorf clarified that the claimant must not focus solely on the objective problem of the patent in suit, but must demonstrate the function of each substituted feature in achieving that objective and explain why the variation performs essentially the same function (Headnote 2). This mirrors the first Schneidmesser question and reads a distinctly German, feature-by-feature technical discipline into the first question of the Dutch test. On the second Plant-e question, the panel held – rather self-evidently – that applying the equivalent element is not obvious where it would require a complete redesign of the claimed device (Headnote 3, para. 263). Beyond this, the court did not deviate from the approach of the LD The Hague.

Endorsement – with a caveat

The endorsement by a German Local Division carries weight. One passage, however, counsels against reading the decision as a landmark ruling: the panel expressly noted that there is no indication that applying a different standard than the Plant-e test would have produced a different result in the case at hand (para. 240). The adoption of the Dutch framework was thus outcome-neutral; the panel did not decide that Plant-e must prevail where the two tests genuinely diverge – for instance on the reference date. That question remains open, ultimately for the CoA. The decision is therefore best read not as a defeat of the German approach, but as a step towards convergence: a German Local Division applying the Dutch framework while injecting German technical rigour into its first question. The direction of travel towards a uniform UPC test for equivalence has become clearer; its final destination has not yet been fixed.