Reliance on a silent technical effect: Application of G 2/21 to semiconductors (T 2465/19)

The Enlarged Board of Appeal (EBA) decision in G 2/21 arose from a case seeking guidance on the evidence requirement for a purported technical effect relied on for inventive step (IPKat). However, in its final order, G 2/21 focussed less on the amount of evidence needed to support an invention, and more on the disclosure requirement for a technical effect relied on for inventive step. Therefore, while the interpretation of G 2/21 has so far predominantly been in Board of Appeal cases in the biotech field (T 0873/21T 1394/21T 0116/18), G 2/21 also has relevance to any case for which a new technical effect, not mentioned in the application as filed, is relied on for inventive step. The Board of Appeal in T 2465/19, for example, cited G 2/21 in a case related to the inventive step of a semiconductor. 

G 2/21 case catch-up: Experimental evidence, the problem solution approach and disclosure of the technical effect

Searching for semiconductors

The referral in G 2/21 related to the evidence requirements for inventive step. The problem solution approach to inventive step employed by the EPO relies on identification of the "closest prior art" with respect to the claimed invention. This often creates a problem for applicants in cases where a purported technical effect requires experimental evidence. In such cases, the embodiment representing the "closest prior art" may be obscure and not known to the inventors at the filing date.  As a consequence, the applicant may fail to include data demonstrating the technical effect of the invention in view of the closest prior art in the application as filed. In such cases, the problem faced by the patentee is a need for experimental evidence that only becomes apparent after the filing date of the application. The problem of post hoc identified prior art was one of the central problem giving rise to the referral in G 2/21:

"it is often necessary, like in this case, to provide post-published evidence (i.e. evidence that was not public before the filing date of the patent in suit and was filed after that date) as proof that the problem has been solved (i.e. that the alleged technical effect is actually achieved). This applies in particular when the objective technical problem has to be reformulated, e.g. with regard to a closest prior-art document previously unknown to the patent proprietor" (T 0116/18, r. 13.2)

Application of G 2/21 outside of biotech

There is currently some debate over the potential relevance of G 2/21 outside the setting of biotech and pharmaceutical inventions. This Kat has previously observed that G 2/21 is likely to be relevant in any field that requires evidence of a technical effect over the closest prior art (IPKat), including software and machine learning invention (T 2465/19).

However, the problem of post-hoc identified prior art may even be relevant to fields for which experimental evidence is not generally required. Even for mechanical inventions, there may be circumstances where the applicant needs to rely on a technical effect for inventive step that was not mentioned in the application as filed. The application as filed may, for example, disclose all the features of the invention, but not describe the advantages of these features. The decision in T 2465/19 demonstrates that G 2/21 is also relevant to these cases.   

T 2465/19: G 2/21 and semiconductors

The case in T 2465/19 related to a patent application (EP2353183, Wolfspeed) for a semiconductor. The issue on appeal was inventive step. The Examining Division (ED) objected that the application as filed was silent about the technical effect of the feature distinguishing the claimed semiconductor from the prior art. For the ED, the distinguishing feature was also merely an arbitrary selection providing no advantage over the closest prior art. In response, the applicant argued that the disclosure of advantages in the description is not a requirement for inventive step, and that the claim should be construed as providing a feature that did provide an advantage. 

On appeal, the Board of Appeal, citing G 2/21, agreed with the applicant that “the technical effect of an invention over the closest prior art need not be explicitly stated in the application, as long as it is derivable from the original application, in particular since the closest prior art may not have been known to the applicant when drafting it” (r. 5.3) This reasoning is in line with other interpretations of G 2/21, including T 0873/21 and T 0116/18. In T 2465/19, the Board of Appeal also construed the claimed feature differently to the ED in view of the application as whole. Following this construction, the Board of Appeal concluded that the feature was not an arbitrary selection, did in fact have an advantageous effect (r. 5.4) and provided an alternative solution on the basis of which inventive step could be acknowledged (r. 5.6).

In this case, it was necessary for the applicant to demonstrate that the feature distinguishing the claimed invention from the prior art had an advantageous technical effect in view of the closest prior art. However, it was not necessary for this technical effect to be recited in the application as filed. The technical field of the invention was also such that experimental evidence of the technical effect need not be provided. As characterised by the Board of Appeal itself, the technical effect could be as straightforward as an alternative solution semiconductor that was “easier to manufacture” (r. 5.5).

Final thoughts

Despite being oft characterised as such, G 2/21 was not really about plausibility (IPKat). By focusing on the disclosure requirement for the technical effect, G 2/21 has become relevant to any patent wishing to rely on an advantage for inventive step that was not disclosed in the application as filed. G 2/21 also arguably did not add much, if anything, to the question of what is the appropriate standard of evidence for inventions in challenging technical fields. Unlike in the UK, the sufficiency requirement remains a low bar for a product claim (IPKat). It also remains necessary to provide some evidence (although less than might commonly be expected) in order to support a claim for a therapeutic use, in view of the higher level of doubt with regards to this type of invention (T 1394/21). Furthermore, providing enough evidence for a purported technical effect for inventive step at the EPO continues to be more challenging in certain technical fields for which there is a lot of potentially relevant prior art such as therapeutic antibodies and machine learning algorithms. G 2/21 did not change the law on any of these issues. 

As interpreted by the Boards of Appeal so far, what G 2/21 did do was to clarify that a technical effect relied on for inventive step does not need to be disclosed in the application as filed (Cf. EPO Guidelines for Examination, H-V, 2.2). This point of law is relevant to any invention. In fact, with regards to disclosure requirements of a technical effect, the case law on this topic may primarily be derived from the software field, where the question is more whether any technical effect of the invention is derivable from the application as filed. We have, by this point, come a long way from "plausibility". 

Further reading

Reliance on a silent technical effect: Application of G 2/21 to semiconductors (T 2465/19) Reliance on a silent technical effect: Application of G 2/21 to semiconductors (T 2465/19) Reviewed by Rose Hughes on Monday, October 02, 2023 Rating: 5


  1. It's important to recognise when the applicant/patentee has made a substantially narrowing amendment to avoid the prior art, and to give them a little bit of credit for that, and not be too harsh on data/advantages in the spec for the new amended claim. If the new claim is a narrow one which won't bother other parties too much in terms of freedom to operate, the system gains little by being too harsh on plausibility/recognition of the problem in the spec. Ultimately the system works best by being lenient in technical areas of little interest to others, and being strict in busy/competitive areas. I believe ED's and OD's recognise that to some extent and are willing to be kind to applicants and patentees as long as no one else is inconvenienced too much. Unfortunately there is no way the EPC or case law can be interpreted in this way, and so the reasoning in decisions has to read as if case law logic was used (but that is not what really happened)

  2. On this topic, let’s keep in mind that the search of the prior art is hindsight-guided since it relies on the content of the original application. This is the motivation put forward by the EPO for the problem-solution approach : minimise the effect of this inevitable hindsight in the assessment of inventive step. In that sense, the terms « subjective technical problem » formulated by the applicant and « objective technical problem » are deeply misleading. The « objective technical problem » based on a closest prior art unknown to the applicant relies on a hindsight-guided search of the prior art. In contrast, the « subjective technical problem » is based on the prior art known to the applicant as the starting point for the invention, which is nothing « subjective » but on the contrary real and relevant.
    When this hindsight factor is paid due attention, arguments submitted during examination to overcome an inventive step objection should be considered admissible provided they are plausible, even if they are not supported in the original application.

  3. This discussion feels like ones I was having 20 years ago. For me, in the context of the EPO's problem-solution approach (EPO-PSA), the expression "closest prior art" (cpa) is unfortunate, best avoided, because outside the confines of EPO-PSA it means something different. Many patent attorneys who are not EPO-PSA specialists import into obviousness arguments at the EPO their understanding of what "cpa" means and that results in much misunderstanding and arm-waving.

    For me, the way to operate EPO-PSA correctly is to give full faith and credit to Applicant's drafting. Applicant decides what is the technical field and what technical problem is solved by the claimed subject matter. The EPO searches relative to that, and quite often finds prior art more relevant than was known to those drafting the patent application. Which of those newly found and more relevant pieces of prior art is the "closest"?

    For me, a piece of art is only eligible for the title "closest" if it is the most realistic "starting point" for a notional skilled person in the field designated by Applicant and addressing the problem announced by Applicant in the application as filed. That filter on eligibility for the status of cpa is, for me, is the way EPO-PSA shuts out inequitable hindsight reasoning and keeps the enquiry objective.

    Of course, as the present debate reveals, application to the claims of the newly discovered art and improved "starting point" can result in Applicant being unable to point to a disclosure in the application as filed of a technical effect specifically relative to the new and improved prior art starting point discovered by the EPO. For me, the G Decision represents a worthy attempt to mediate between reasonable legal certainty for the public and "fair" protection for the inventor's contribution to "the art" even while preserving an obviousness enquiry that is strictly objective and free from ex post facto reasoning and prejudice.

    We have come a long way from the UK's pre-1978 attitude, that obviousness is an enquiry that cannot reasonably be undertaken ex Parte, but only in the course of full-blown judicial revocation actions with full x-exam of tech experts fielded by the opposing sides. EPO-PSA, especially in EPO opposition proceedings, continues to manage the obviousness enquiry far better than anything else available elsewhere, no?

  4. @Anonymous
    Indeed the definition of the technical field in the application is key. And I mean by "technical field" a reference to a certain field of use, which can also equated to the "art" of the skilled person.
    In the discussions about the "closest prior art" and the "technical problem", be it subjective or objective, a missing but key element is generally the "art" of the skilled person. This may sound surprising, since the skilled person is a most critical notion and it is explicit in the EPC (as in other patent laws), not just for inventive step but also for sufficiency and implicit for novelty. Whereas the PSA and the CPA are not in the EPC.
    In my view, the presentation of the PSA as a three-step approach starting with the CPA is defective because it skips the preliminary crucial step which is the identification of the « art » to which Art 56 refers.

  5. Mr Hagel, do you not think that argument about what is the involved "art" is part of the debate that takes place for fixing what is a fair prior art "starting point"? Suppose that you are involved, and think that the other side's argumentation for D1 as its starting point is defective because D1 is not in the correct "art". What is stopping you arguing that point, to get D1 disqualified as the "cpa".

  6. @Max Drei

    You are absolutely right, defining the « art » of the skilled person is the crux of the debate regarding the closest prior art. Saying that the closest prior art is supposed to relate to a use or purpose similar to the claimed subject matter implies that it belongs to the « art ». This tends to refer the « art » to a context of use, more than to a broadly defined technical field. If I take the example of a capacitor designed for high voltage grids, the skilled person is skilled in the art of high voltage grids. Any design choice is controlled by the high voltage context.

    I think it makes sense to refer to the « art » in the assesment of inventive step First, for the simple reason that this is the notion laid out by the explicit language of the EPC. The term « not obvious » is so vague in itself that it is meaningless without a definition of the art (and of the skill level) of the skilled person. In addition, beyond the identification of the CPA, the identification of the « art » is key to understand the « technical problem ». I note here that the use of the singular form for the « problem » although it is general is grossly simplistic. This is so because in any art, the « problem » is not just about obtaining a very specific effect, it also requires the host of constraints relevant to this art (and thus known to the skilled person), often implicit in the application, to be met for the purported effect to be achieved. This is a very important consideration in the assesment of inventive step, as the skilled person would not consider prior art which fails to meet these constraints. Which is why my general recommendation for drafting practice is to carefully document in the application the context of use of interest to the applicant and the relevant technical effects/advantages.

    My emphasis on the « art » certainly draws on my decade-long experience as a corporate patent lawwyer in several companies of the mechanical/physics sectors. I have always been struck by how narrowly specialised the real-life skilled people are. This tends to be ignored of course by examiners but also by practitioners in private practice.

    This reminds me of a story. I was involved long time ago in meetings between experts of different fields : the car industry and the oilfield industry (which requires equipment fit for use in the high temperature, very high pressure environment of deep wells). The expectation was to share information regarding electronics compatible with high temperatures. But it became clear very quickly that no common ground could be found, because of the huge differences between the respective contexts (primarily a ratio of 1:1000 or more as to production volumes and costs).


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