Part 1: Inventive step at the EPO

The European Patent Office (EPO) opens its guidelines on inventive step by saying:

The term "obvious" means… something which does not involve the exercise of any skill or ability beyond that to be expected of the person skilled in the art. - EPO Guidelines March 2024 Ed, G-VII 5.

The EPO has, over time, developed a framework known as the “problem-solution approach” to provide an objective way to assess whether a claimed invention is obvious. This is done by evaluating whether the prior art points to the claimed features as solving an “objective technical problem”.

To summarise, the problem-solution roadmap involves:

This first in a series of two articles reviews each stage of the roadmap in turn and provides practical advice for applicants seeking patent protection in Europe.

The second article in the series goes through the approach using a worked example from the field of textiles and provides a “watch this space” comment on the somewhat different legal framework recently adopted in post-grant proceedings in Europe, at the new Unified Patent Court, for the inventive step assessment.

The closest prior art

The first step in the problem-solution approach is to choose the “closest prior art”.

The closest prior art is that which in one single reference discloses the combination of features which constitutes the most promising starting point for a development leading to the invention. In selecting the closest prior art, the first consideration is that it must be directed to a similar purpose or effect as the invention or at least belong to the same or a closely related technical field as the claimed invention. In practice, the closest prior art is generally that which corresponds to a similar use and requires the minimum of structural and functional modifications to arrive at the claimed invention (see T 606/89). - EPO Guidelines March 2024 Ed, G-VII 5.1

• The closest prior art is the starting point from which we assess inventive step.
• Sometimes it is an entire document, but often it is a single embodiment within a document (e.g., Example 4 when there are eight Examples; or Figure 5 when there are ten Figures).
• The criteria for which document is selected are, in order of importance: field, purpose, structure.
• Other things to consider include: does the document contain any negative statements teaching away from any of the features in the claim object? Does the document already contain pointers to the problem? Which choice of closest prior art needs the least explaining?

In some cases there are several equally valid starting points for the assessment of inventive step, e.g. if the skilled person has a choice of several workable solutions, i.e. solutions starting from different documents, which might lead to the invention. If a patent is to be granted, it may be necessary to apply the problem-solution approach to each of these starting points in turn, i.e. in respect of all these workable solutions. However, applying the problem-solution approach from different starting points, e.g. from different prior-art documents, is only required if it has been convincingly shown that these documents are equally valid springboards. In particular in opposition proceedings the structure of the problem-solution approach is not that of a forum where the opponent can freely develop as many inventive step attacks as desired in the hope that one of said attacks has the chance of succeeding (T 320/15, Reasons 1.1.2). - EPO Guidelines March 2024 Ed, G-VII 5.1

• In examination proceedings, it is normally the Examiner who chooses the closest prior art. An applicant may question that choice and can sometimes persuade the Examiner that another document is a more appropriate starting point and/or the Examiner’s selected starting point leads to artificial results or requires the benefit of hindsight.
• Unless there are very strong reasons for dismissing the starting point selected by the Examiner, the better option is often to work from the same starting point as the Examiner. At the time of writing, we have begun seeing Examiners argue that “if a claim is obvious starting from document X, document X must be the closest prior art”. While this represents a flawed assessment, going with the grain on this point while showing how the claim is still not obvious, may be the more persuasive approach.
• The choice of closest prior art is contested more often in post-grant opposition proceedings than in pre-grant examination proceedings.
• In opposition proceedings, an opponent may tactically launch several problem-solution inventive step attacks by starting from several different closest prior art documents in turn. Only those that present realistic springboard to the present invention are likely to be accepted as valid starting points.
• The choice of closest prior art will drive the definition of the objective technical problem to be solved (see below). Opponents will frequently try to have the problem defined as “merely providing an alternative” to the prior art, which means the skilled person does not need as much motivation to reach the claimed solution.

The next steps: it’s all about defining the objective technical problem to be solved

Once we have the closest prior art, there are three steps that sometimes are rolled under one umbrella: finding the “distinguishing feature(s)”, defining the “technical effect” of those features, and determining the “objective technical problem” solved.

As the EPO explains:
[After selecting the closest prior art] one establishes in an objective way the technical problem to be solved. To do this one studies the application (or the patent), the closest prior art and the difference (also called "the distinguishing feature(s)" of the claimed invention) in terms of features (either structural or functional) between the claimed invention and the closest prior art, identifies the technical effect resulting from the distinguishing features, and then formulates the technical problem. - EPO Guidelines G-VII 5.2

• Finding the distinguishing features, then establishing what technical effect they have, enables us to define what problem the invention is solving that is not solved by the closest prior art.
• This is the position from which we determine obviousness: would it have been obvious to the skilled person to modify the closest prior art in such a manner as to arrive at the claimed subject matter in the expectation of solving the problem? In assessing this, the disclosure of the closest prior art can normally be modified in view of the teaching of one other document - but it is unusual to be allowed to use more than one other “combination” document (see below).

Distinguishing features

The distinguishing features over the closest prior art can be structural and/or functional.

Technical effect

The technical effect must be a direct result of the distinguishing feature(s). We must be able to show that feature X causes effect Y.

It is sometimes the case that the existence of the effect can be implicit or self-evident. For example, a process with fewer steps is clearly more efficient than a more convoluted process.

However, in many cases, evidence of the existence of the technical effect is required. There are a wide range of way that the existence of the technical effect can be demonstrated, such as by pointing to post-filing publications. However non-technical evidence, such as an indication that an invention has been commercially successful, is less likely to be found convincing.

European Examiners find comparative evidence the most convincing evidence of the existence of a technical effect. For example, evidence comparing the prior art which lacks feature X, with a directly comparable product that includes feature X, is highly persuasive in demonstrating that feature X causes effect Y. This is especially true in post-grant opposition and appeal proceedings where the strength of the evidence showing the existence of a technical effect is often key to whether a patent is maintained or revoked.

As the content of the prior art is rarely known at the time of filing, it is never going to be possible to provide a comprehensive set of comparative evidence in the application as filed. However, the more evidence that can be included at the outset the better. Ideally the evidence will vary a single feature at a time to enable effects associated with each feature to be identifiable and will demonstrate that the effect is obtained across the scope of the claims by providing multiple examples.

Even if a technical effect is not conclusively demonstrated in the application as filed, it can still be taken into account and, if necessary, supplementary evidence provided after filing to support its existence, when the effect can be deduced from the application as filed. The EPO Guidelines say:

As a matter of principle any effect provided by the invention may be used as a basis for the reformulation of the technical problem, as long as said effect is derivable from the application as filed (see T 386/89). It is also possible to rely on new effects submitted subsequently during the proceedings by the applicant, provided the skilled person, having the common general knowledge at the effective filing date in mind, and based on the application as originally filed, would derive said effect as being encompassed by the technical teaching and embodied by the same originally disclosed invention (see G‑VII, 11 and G 2/21). - EPO Guidelines G-VII 5.2

There is recent case law on the admissibility of evidence submitted after the application was originally filed. In G2/21, the Enlarged Board of Appeal ruled that “a patent applicant or proprietor may rely upon a technical effect for inventive step if the skilled person having the common general knowledge in mind, and based on the application as originally filed, would consider said effect as being encompassed by the technical teaching and embodied by the same originally disclosed invention.” – r. 94, G2/21.

What is meant by this remains something of an open question. Subsequent Board of Appeal decisions reveal a broadly pro-applicant trend. In particular, in T 116/18 (decision handed down in November 2023):

• The Board confirmed that “it is not necessarily a precondition … that the application as filed contains experimental proof that the purported technical effect is actually achieved”
• It is “not necessarily a precondition … that the application as filed contains a positive verbal statement about the purported technical effect”
• In opposition, it seems that the burden of proof will rest with the opponent to show why the skilled person would have a legitimate reason to doubt a technical effect can be achieved

However, in practice it is helpful as a minimum for there to be some pointer in the application as filed to the technical effects later relied upon. The existence of that pointer will enable the applicant to produce additional supporting evidence later if needed. The practical upshot for applicants, during the drafting process, is to include statements about advantages of the features discussed in the application as originally filed. Describing Feature A provides basis for claiming Feature A if needed in prosecution; saying “Feature A has been found to be useful in facilitating the provision of advantage Z” associates Feature A with a technical effect to establish inventive step. Wherever possible, the application as filed should include evidence backing up the statements made and demonstrating the existence of advantages associated with the features present in the claims.

The objective technical problem to be solved

Importantly, the problem does not have to be related to an aim discussed in the Background section of the application as originally filed. It is formulated starting from the prior art cited by the Examiner in examination or by the opponent in opposition:

The objective technical problem derived in this way may not be what the applicant presented as "the problem" in the application. The latter may require reformulation, since the objective technical problem is based on objectively established facts, in particular appearing in the prior art revealed in the course of the proceedings, which may be different from the prior art of which the applicant was actually aware at the time the application was filed. - EPO Guidelines G-VII 5.2

• Often the objective technical problem is formulated simply as “how to obtain [the technical effect]”.
• Although it can be difficult to predict what art will be cited in prosecution, drafters should consider including something about technical effects of key features in the application as filed.

The final question: is the solution to the problem obvious?

Once the problem has been defined, one asks whether the solution provided by the claim is obvious.

First: is it obvious over the closest prior art, taken alone but in view of the common general knowledge of the skilled person?

Then: is it obvious over the closest prior art when combined with one of the other cited documents?

In determining whether it would be obvious to combine two or more distinct disclosures, the examiner also has regard in particular to the following:

• whether the content of the disclosures (e.g. documents) is such as to make it likely or unlikely that the person skilled in the art, when faced with the problem solved by the invention, would combine them – for example, if two disclosures considered as a whole could not in practice be readily combined because of inherent incompatibility in disclosed features essential to the invention, the combining of these disclosures is not normally regarded as obvious;
• whether the disclosures, e.g. documents, come from similar, neighbouring or remote technical fields… - EPO Guidelines G-VII 6

• Are the disclosures structurally and/or functionally incompatible in some way?
• Is the other document from a very remote art field from the first?
• Does the other document teach a different solution, or teach away from the claimed solution?

Under normal circumstances, it is not permissible to combine more than one other document with the closest prior art. One looks at the closest prior art plus each other cited document in turn. One does not look at them all together.

There is an exception, which is known as “partial problems”.

Partial problems

The exception is when there are two (or more) unrelated distinguishing features over the closest prior art, solving two distinct and unrelated problems.

In the context of the problem-solution approach, it is permissible to combine the disclosure of one or more documents, parts of documents or other pieces of prior art (e.g. a public prior use or unwritten general technical knowledge) with the closest prior art. However, the fact that more than one disclosure must be combined with the closest prior art in order to arrive at a combination of features may be an indication of the presence of an inventive step, e.g. if the claimed invention is not a mere aggregation of features (see G‑VII, 7).

A different situation occurs where the invention is a solution to a plurality of independent "partial problems" (see G‑VII, 7 and 5.2). Indeed, in such a case it is necessary to separately assess, for each partial problem, whether the combination of features solving the partial problem is obviously derivable from the prior art. Hence, a different document can be combined with the closest prior art for each partial problem (see T 389/86). For the subject-matter of the claim to be inventive, it suffices however that one of these combinations of features involves an inventive step. - EPO Guidelines G-VII 6

• “Partial problems” arise when 2 unrelated distinguishing features solve 2 unrelated problems.
• In this case, one must use the same closest prior art (call it D1) for both problems, but it is permissible to combine D1+D2 for feature A that solves problem No. 1; then combine D1+D3 for feature B that solves problem No. 2.

Looking ahead: Article No. 2

See the second article in this series for a worked example of how to argue for inventive step under the problem-solution approach, plus a comment on the interesting new approach adopted by the new Unified Patent Court.

This article does not constitute legal advice. For assistance in patent matters, please get in touch with the author or reach out to your usual contact at Abel + Imray.