3.4.1 General

The boards have consistently held that, where more than one document is cited as the closest prior art, the one which must be deemed the closest is that which provides the skilled person with the most promising springboard to the invention, i.e. the one starting from which the subject-matter of the invention is rendered most obvious (T 656/90, T 824/05, T 1755/07, T 698/10, T 1940/16).

In T 698/10 the board held that the expression "closest prior art" did not mean that it must be sufficiently close to the claimed invention on an absolute basis, but only that it must be relatively closer to the claimed invention than the other prior-art disclosures, i.e. it was selected as the most promising starting point - or the most promising springboard towards the invention.

In T 694/15 the board was of the opinion that the terminology "closest prior art" was somewhat misleading and that it was perhaps preferable to use the terminology "starting point (in the prior art)". It could be economical to start from prior art that is in some sense close to the invention, in the hope that the consideration of this single starting point would be enough to establish whether the claimed subject matter would have been obvious. However, if this failed, before arriving at the conclusion that the subject matter would not have been obvious, it was necessary to consider other possible starting points. The board considered that what was decisive for establishing obviousness was not the closeness of the starting point but the overall likelihood of the path, given the starting point.

However, when assessing inventive step, care must be taken to avoid an ex-post-facto approach. A skilled person endeavouring to arrive at a simple construction is unlikely to begin by using prior art relating to an exceptional embodiment with a complex mechanism, and then to omit this mechanism from the invention (T 871/94). In T 2114/16 the board found that an inventive step objection based on selecting a clearly disadvantageous starting point from prior art document E22 would necessarily be contaminated by hindsight, since this choice could only be motivated by the previous knowledge of the claimed invention. Following the problem-solution approach, the skilled person would start from the teachings of the exemplary embodiments of E22.

In T 1599/14 the board considered that there was nothing to prevent the appellant (opponent) from choosing as a starting point for its argument a piece of prior art or an embodiment that was less promising than other disclosures or embodiments which, on the face of it, were closer to the claimed subject-matter. See also T 405/14 in which the board concluded that every objection of lack of inventive step had to be assessed on its own merits and that a document selected as starting point could not be excluded only because some seemingly more promising item of prior art was available.

In T 1841/11 the board stated that even if prior art relating to the same purpose was available, it was not excluded that a document relating to a similar purpose might be considered to represent a better – or at least an equally plausible – choice of closest prior art, provided that it would be immediately apparent to the skilled person that what was disclosed in the document could be adapted to the purpose of the claimed invention in a straightforward manner, using no more than common general knowledge. See also T 1160/12, T 1518/17.

In T 816/16 the board held that the question of whether a particular disclosure was closer or further removed in relation to the subject-matter claimed was irrelevant. Starting the assessment of inventive step from the "closest prior art" served the purpose of avoiding the need to consider a multitude of potential starting points as it could be assumed that wherever a particular claimed subject-matter involved an inventive step having regard to this "closest prior art", it would all the more involve an inventive step when the assessment was based on a disclosure which was not the "closest" prior art.

In T 1518/17 the board held that where two documents were both suitable to serve as the closest prior art, it was necessary that an inventive step be demonstrated with respect to each. A finding of obviousness in respect of one document would necessarily lead to the conclusion that the requirements of Art. 56 EPC were not met even if the same exercise on the basis of the other document would lead to a different conclusion. See also T 23/17.

In T 787/17 the board held there was no need for special justification, e.g. on the basis of the skilled person's considerations. In particular, whether such an element gave any indication as to how to solve the objective technical problem was irrelevant to its selection as a starting point, for the simple reason that the objective technical problem could only be defined on the basis of the starting point. Nor was there any need to justify why the skilled person would proceed from one particular embodiment among a large number of embodiments in a pre-published document. Each of the embodiments constituted an element of the prior art that was known per se to the (notional) skilled person and could therefore equally serve as a starting point.