T 0405/14 - The notion of closest prior art

Key points

• The applicant defends inventive step by arguing that “the skilled person would never start from document D2 when document D1 was available”.
• The Board rejects this argument “in its very principle. The fact that D1 is available does not make an objection which would otherwise have been considered possible when starting from D2 any less pertinent.”
• The Board: “More fundamentally, the notion of "closest prior art", as it has been developed by the case law of the boards of appeal, appears to encompass two different meanings, depending on the outcome of the objection raised under Article 56 EPC.” 
• “On the one hand, when concluding that a claimed invention is inventive, the notion of "closest prior art" seems to rely on the assumption that there exists a metric defining the distance between items of prior art and the invention, and that an invention which is 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, are not so close.”
• “The second meaning is often formulated in terms of a requirement for the "closest prior art" to deal with the same problem as the invention. This is intended to avoid hindsight leading to a finding that inventive step is lacking. Here, there is no requirement that the "closest prior art" be unique, because the basic rule is that an invention lacks inventive step if it would have been obvious to the skilled person, without hindsight, for any starting point.”
• “all items of prior art considered as starting points which allow the elaboration of a realistic attack under Article 56 EPC may be considered to qualify as "closest prior art", although this currently accepted terminology is somewhat misleading. The approach thus excludes any abstract notion of metric. It follows that every objection of lack of inventive step has to be assessed on its own merits and that a document selected as starting point cannot be excluded only because some seemingly more promising item of prior art is available.”
• As a comment, the Board's reasoning entirely makes sense to me. To cite G.Szabo in EIPR 1986 8(1), p.293-303: " If the invention is, on the other hand, upheld in spite of the existence of the closest art, other less relevant citations need hardly be considered as starting points for such challenge. [...] An opponent may nevertheless always try to launch an attack based on a different document, and if successful, this would become the closest art in the given circumstances." 

EPO T 0405/14 - link

Starting from document D2

17. The appellant held that the skilled person would never start from document D2 when document D1 was available. This view relied on the view that document D1, in addition to sharing many features with the claimed invention, also addressed the same problem, i.e. how to test speed sensors relying on Hall effect or magneto resistive properties.

18. The argument is rejected in its very principle.

The fact that D1 is available does not make an objection which would otherwise have been considered possible when starting from D2 any less pertinent.

More fundamentally, the notion of "closest prior art", as it has been developed by the case law of the boards of appeal, appears to encompass two different meanings, depending on the outcome of the objection raised under Article 56 EPC.

On the one hand, when concluding that a claimed invention is inventive, the notion of "closest prior art" seems to rely on the assumption that there exists a metric defining the distance between items of prior art and the invention, and that an invention which is 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, are not so close. Independently of the fact that the jurisprudence does not define any such metric beyond indicating what criteria might be considered relevant to it (common features, similar purpose, ...), there are frequent situations in which the identification of a unique closest or best starting point is not straightforward or even possible.

The second meaning is often formulated in terms of a requirement for the "closest prior art" to deal with the same problem as the invention. This is intended to avoid hindsight leading to a finding that inventive step is lacking. Here, there is no requirement that the "closest prior art" be unique, because the basic rule is that an invention lacks inventive step if it would have been obvious to the skilled person, without hindsight, for any starting point.

Furthermore, the assumptions underlying the concept of "closest prior art" do not accord well with the general principle, derived from the case law, that, in order to be successful, an objection of lack of an inventive step must establish a complete logical chain of considerations which would lead the skilled person to the claimed subject-matter. This basic requirement opens the door to the elaboration of various scenarios under the well-established problem-solution approach, and possibly relying on different items of prior art as starting points, not even limited to items of prior art dealing with the same or similar problem so long as hindsight is avoided.

19. The question to be answered, when selecting a starting point, is, thus, essentially, whether it allows such a realistic objection of lack of inventive step to be raised. In case T 2057/12, the present Board, in a different composition, elaborated on the risks that could result from a rigid application of the criteria developed by the jurisprudence of the boards of appeal when selecting this starting point. Under certain circumstances, this approach may even affect the objectivity of the analysis to be made (cf. T 2057/12, Point 3.2.2). Experience teaches that a document which shares a common purpose with a claimed invention, as well as a large number of features, in order to solve the same or a similar problem, will not necessarily allow a convincing objection of obviousness to be raised against that invention, whereas said invention may indeed result, without hindsight, in an obvious manner from an apparently less promising item of prior art. In this respect, all items of prior art considered as starting points which allow the elaboration of a realistic attack under Article 56 EPC may be considered to qualify as "closest prior art", although this currently accepted terminology is somewhat misleading. The approach thus excludes any abstract notion of metric. It follows that every objection of lack of inventive step has to be assessed on its own merits and that a document selected as starting point cannot be excluded only because some seemingly more promising item of prior art is available.

20. In the present situation, although document D2 shares fewer features with the claimed invention than D1 does, it is nevertheless a valid starting point. It is, in particular, stressed that D2 explicitly relates to a self-testing device that can be used for speed measurements (cf. column 4, lines 25-29). It is further stressed that claim 1 does not specify the kind of object of which the speed is to be measured. It thus also encompasses debris sensors of the kind disclosed in D2.