3. Closest prior art
3.3. Several workable routes to the invention
If the skilled person has a choice of several workable routes, i.e. routes starting from different documents, which might lead to the invention, the rationale of the problem-solution approach requires that the invention be assessed relative to all these possible routes, before an inventive step can be acknowledged (T 967/97, Catchword I; see also T 323/03, T 21/08, T 1437/09, T 308/09, T 1742/12, T 1261/14, T 1339/14, T 259/15, T 62/16, T 1076/16, T 1750/19, T 397/20, T 2029/21, T 1654/22). This principle stems from the fact that the inventive step requirement under Art. 56 EPC applies to the state of the art as a whole, as defined in Art. 54(2) EPC (see e.g. T 72/18, T 865/21).
Conversely, if the invention is obvious to the skilled person in respect of at least one of these routes, then an inventive step is lacking (T 967/97, Catchword II; see also T 558/00, T 308/09, T 1437/09, T 2418/12, T 1570/13, T 62/16, T 64/16, T 2443/18, T 2411/18, T 1012/19, T 1654/22). In T 967/97 it was further stated that, if an inventive step was to be denied, the choice of starting point needed no specific justification. In T 261/19 the board stated that this was because the claimed invention must then, as a general rule, be non-obvious having regard to any prior art (see also T 696/19, T 138/21, T 981/22).
The board in T 1742/12 held that a piece of prior art may be so remote from the claimed invention, in terms of intended purpose or otherwise, that it could be argued that the skilled person could not conceivably have modified it so as to arrive at the claimed invention. Such prior art might be referred to as "unsuitable". However, this did not prohibit the consideration of an inventive-step assessment starting from a piece of prior art with a different purpose (see also T 855/15, T 2304/16, T 1294/16, T 2443/18, T 1112/19). In T 1733/21 the board stated that while prior art directed to the same technical effect as the invention might seem promising initially, this did not necessarily mean that the prior art should be taken into account. Otherwise, prior art which was silent on the intended effect would never constitute a valid starting point, and that would go against established practice.
If a piece of prior art is "too remote" from an invention, it should be possible to show that the invention is not obvious to a skilled person having regard to this piece of prior art (T 855/15, T 2057/12, T 2304/16, T 154/17). A generically different document cannot normally be considered as a realistic starting point for the assessment of inventive step (T 870/96, T 1105/92, T 464/98, T 2383/17).
In T 176/89 the board concluded that the closest prior art comprised two documents in combination with each other. It found that, exceptionally, the two documents had to be read in conjunction; they had the same patentee, largely the same inventors, and clearly related to the same set of tests. As a rule, however, when assessing inventive step, two documents should not be combined if, in the circumstances, their teaching is clearly contradictory (see also T 487/95).
The board in T 2579/11 ruled that there was no justification for disregarding a priority application and choosing a subsequent application as the closest prior art simply because the description in the subsequent application was by and large more detailed.
Public prior use may be used as the closest state of the art (T 1464/05, see also T 1054/18).
In T 172/03 the board held that the term "state of the art" in Art. 54 EPC 1973 should be understood as "state of technology", and that "everything" in Art. 54(2) EPC 1973 was to be understood as concerning the information which was relevant to a field of technology. It could hardly be assumed that the EPC envisaged the notional person skilled in the (technological) art would take notice of everything in all fields of human culture and regardless of its informational character.
However, the board in T 2101/12 considered that the interpretation of Art. 54(2) EPC given in T 172/03 was incorrect. According to the board in T 2101/12, the legislator would have used a different term if such meaning had indeed been intended. It held that the wording of Art. 54(2) EPC was clear and required no interpretation. Art. 54(2) EPC itself contains no limitation according to which a non-technical process, such as the signing of a contract at the notary's office, may not be considered state of the art (see also T 1049/19).
In T 1148/15 the board pointed out that the assumption that the remaining prior art was less relevant than the item of prior art identified as the closest may turn out to be wrong, for instance if it could be convincingly shown that the skilled person would have arrived at the claimed subject-matter in an obvious manner when starting from another item of prior art but not when starting from the identified closest prior art. In that situation, or even in case of doubt, the problem-and-solution approach may have to be repeated for any prior art that also qualifies as a suitable starting point.
In T 405/14 the board stated that the notion of "closest prior art", as it had been developed by the case law of the boards of appeal, appeared to encompass two different meanings, depending on the outcome of the objection raised under Art. 56 EPC. On the one hand, when concluding that a claimed invention was inventive, the notion of "closest prior art" seemed to rely on the assumption that there existed a metric defining the distance between items of prior art and the invention, and that an invention which was not obvious from the "closest prior art" would a fortiori not be obvious with regard to all other items of prior art which, by definition, were not so close. The second meaning was often formulated in terms of a requirement for the "closest prior art" to deal with the same problem as the invention. This was intended to avoid hindsight leading to a finding that inventive step was lacking. The board concluded that here there was no requirement that the "closest prior art" be unique, because the basic rule was that an invention lacked inventive step if it would have been obvious to the skilled person, without hindsight, for any starting point (see also T 1012/19).
In T 97/14 the board held that a reasoned objection of lack of inventive step must establish the state of the art and set out, in a clear and complete manner, which features of the claimed invention were known from the prior art and where those features could be found in the prior art. In other words, a proper feature mapping was required. This was all the more important when the objection relied on non-documentary prior art, because such evidence was more difficult to verify.
In T 1012/19 the board noted that the established practice in some fields of technology was indeed to cut down a plurality of feasible starting points to a single closest prior art. Nevertheless, this was often an ideal situation and that, in praxis, more documents may actually be considered in the first step of the problem-solution approach. The board subscribed to the view taken in a consistent line of decisions that if the skilled person had a choice of several workable routes, i.e. routes starting from different documents which might lead to the invention, the rationale of the problem-solution approach required that the invention be assessed relative to all these possible routes, before an inventive step could be acknowledged.
In T 335/20 the board stated that when applying the problem-solution approach in the assessment of inventive step, information that was not disclosed in the prior art was considered in determining the distinguishing features, the resulting technical effect, and the formulation of the objective technical problem to be solved. To what extent the claimed subject-matter differed from the disclosure(s) in the prior art was thus relevant when determining the distinguishing features. The teaching towards the distinguishing features might then come from another prior art document or from the common general knowledge of the skilled person. In the case in hand, D9's lack of disclosure as regards implementation of the proposed PGRN replacement therapy did not therefore disqualify it from being the starting point for the assessment of inventive step.
In T 1090/21 highlighted that the number of suitable prior-art documents might depend on the breadth of a claim, so that a broad claim might lead to a situation where several documents were equally valid starting points. The same was true in a highly competitive technical field where many closely related prior-art documents had been published. However, the fact that several documents might be proposed as the closest prior art was not incompatible with the problem-solution approach.
The board in T 1888/21 adhered with the view of the board in T 405/14, at least insofar the selection of a single starting point as a matter of principle would not correspond to the real situation encountered by the notional skilled person. On the contrary, an inventor seeking to achieve a given goal would rather find it natural to maximise their chances of success by trying more than one promising and realistic starting point.
- T 1632/22
In T 1632/22, In ex parte case T 1632/22, the application related to liveness detection in relation to authentication, e.g. when unlocking a phone based on a face image. The application proposed to categorise the images as a function of their "quality" and to use different liveness detectors for each quality type. The examining division concluded there was a lack of inventive step over D1 (face authentication).
With an amendment in substance to define the quality parameter used to define the quality type, the new feature of claim 1 was not disclosed in D1. The board saw only two differences between claim 1 and D1 which might support the presence of an inventive step, namely that the claimed method was used for liveness detection and that it considered also quality parameters other than those disclosed for the "specialized classifiers" of D1. For the appellant, D1 did not qualify as the closest prior art as it was concerned with authentication rather than with liveness detection.
In the board’s view, the novelty requirement provides that no patent can be granted for anything that is already known. The inventive step requirement raises the bar to a patent by also excluding matter which is obvious over what is known. That which is obvious to the skilled person cannot depend on anything that the skilled person does not know yet. In particular, what is obvious at the filing date of a patent application cannot depend on the content of that patent application. Conversely, an argument that a skilled person having regard to some piece of prior art will find something to be obvious cannot be rebutted on the basis of what the application says. In particular, the application cannot be invoked to limit the prior art under consideration or the expertise of the skilled person (their "art") on the basis of the stated "field of the invention". That essentially any piece of prior art can be considered in an inventive step analysis has been stated several times in the case law. The definite articles in the phrase "the person skilled in the art" in Art. 56 EPC are not meant to limit the relevant "arts". Any successful rebuttal of an inventive step objection must address the obviousness argument directly, without reference to the application.
It is a matter of efficiency when assessing inventive step to consider only persons skilled in arts related to the claimed invention, and, consequently, only prior art which such a person may have regard to. The board considered that a person skilled in some art may well have regard to prior art from a field which is not, in a narrow sense, their "own field". It is reasonable to assume, for instance, that persons skilled in one field will typically keep themselves informed about developments in related fields, and in this sense have regard to prior art in related fields. The board disagreed with T 646/22 and held that in principle, all problems which the skilled person would have addressed (or been asked to address) based on the prior art alone are valid ones. In the present case, the board assumed a person skilled in liveness detection methods. Such a person was, generally, interested in improving, or finding alternatives to, known liveness detection methods, based on the knowledge that known methods have known pitfalls. Liveness detection for authentication and authentication were closely related technical areas. The board noted that it was typical to try adapting developments in neighbouring fields to the own area of interest. It was certainly common practice in image processing, in particular when the images were of the same type. Thus, in the board's judgement, the person skilled in the art in liveness detection would have regard to D1 and would have reason to adapt its solution to liveness detection in a way leading to the invention according to claim 1 of the main request before the examining division. The current requests differed from that request ("quality parameter").
Finally, the board noted that during examination a relatively large number of documents were cited, some of them concerned with liveness detection, but were not discussed in the decision. A positive decision on inventive step could not be issued before at least these documents have been discussed (Remittal).
- T 1078/23
In ex parte case T 1078/23, the decision of the examining division refused the European patent application for, at least, lack of inventive step; the examining division considered prior-art document D1 "to be the prior art closest to the subject-matter of claim 1". The appellant submitted that document D1 failed to disclose at least feature (c) of claim 1. So, document D1 – in spite of belonging to the same technical field as the present application – was not an appropriate starting point; the skilled person would rather choose document D5.
In the board’s view, the appellant's argumentation was not convincing. First, the board considered, in agreement with T 787/17, T 967/97, T 1112/19, T 449/23, and contrary to e.g. T 2057/12, T 2759/17 or the conclusions drawn in the first-instance decision of the Unified Patent Court UPC_CFI_1/2023 of the Central Division Munich (point 8.6), that no specific justification for the choice of a starting point for the assessment of inventive step is necessary if inventive step is to be denied, since the claimed subject-matter must be inventive over any state of the art according to Art. 56 EPC. Moreover, it is not the task of the skilled person, who is the person qualified to solve the underlying objective technical problem according to the problem-solution approach, to "choose a document as the closest prior art" (see e.g. T 1450/16). Selection criteria such as the "intended purpose" of the claimed subject-matter thus constitute merely a matter of efficiency for the deciding body.
The board added that a selected starting point might indeed turn out to not be suitable for denying inventive step if, for example, the resulting objective technical problem formulated on the basis of that starting point was an unrealistic or artificial one. But this did not mean that a starting point was to be disqualified as unsuitable right from the outset. Nor was it relevant in that context whether other pieces of prior art, such as document D5, were "relatively closer" to the claimed subject-matter, as argued by the appellant.
Document D1 belonged to the application's technical field; specifically it disclosed features (a) and (b). The fact that D1 did not disclose feature (c), did however not preclude it from being an appropriate starting point for the assessment of inventive step.