6. Ex post facto analysis

Many decisions of the boards of appeal warn against an ex post facto approach when assessing inventive step (see also the Guidelines G‑VII, 8 – March 2022 version). This applies especially to inventions which at first sight seem obvious, to combination inventions and where the proposed solution is supposedly "simple". Correct application of the problem and solution approach avoids this inadmissible ex post facto analysis which draws on knowledge of the invention (T 24/81, OJ 1983, 133; T 564/89; T 645/92; T 795/93).

When assessing inventive step, an interpretation of the prior art documents as influenced by the problem solved by the invention, where the problem was neither mentioned or even suggested in those documents, must be avoided, such an approach being merely the result of an a posteriori analysis (T 5/81, OJ 1982, 249; T 63/97; T 170/97; T 414/98).

In T 970/00 the board stated that any ex post facto analysis, and in particular any conclusion going beyond what the skilled person would have objectively inferred from the prior art, without the benefit of hindsight knowledge of the invention, is of necessity at variance with a proper application of the problem and solution approach. Any attempt to interpret the disclosure of the closest prior art so as to distort or misrepresent, based on hindsight knowledge of the invention, the proper technical teaching of the disclosure in such a way that it artificially meets specific features recited in the claim under consideration must fail, especially as this would risk unfairly and tendentiously concealing the technical contribution of the invention and prejudice the subsequent objective determination of the technical problem solved by the claimed invention (see also T 266/07, T 1486/10).

In T 2201/10, the board found that the examining division had taken an ex-post-facto approach to analysing the facts. Even assuming that the proposed solution could be derived from common general knowledge, it went against the very essence of the teaching in the closest prior art and, therefore, would not realistically have been chosen. The problem and solution approach required that documents not relating to the technical field of the invention be disregarded, and it also precluded any analysis according to which the skilled person would have modified the closest prior art in a manner contrary to its very purpose. In other words, a finding that a claimed invention deviated from what was, in light of the aim pursued, the essence of a prior-art disclosure was enough by itself to conclude that it was inventive over that prior art (see also T 2057/12).

In T 855/15 the board considered that for the assessment of obviousness a consideration as to what the skilled person would do, in particular whether the skilled person "would select" a particular document in order "to arrive at the invention as claimed" would amount to hindsight reasoning, because the skilled person would have to be assumed to know the invention before an argument could be made as to what he would do in order "to arrive at" it. The board in T 2057/12 agreed with the board in T 855/15 insofar as the closest prior art belonged to the same or a neighbouring technical field of the skilled person or to his common general knowledge. Argumentation or evidence should be provided as to why the skilled person in a specific technical field would have indeed envisaged selecting a document in a remote field of technology as closest prior art or whether he would indeed have considered adapting a prior-art disclosure originating from his technical field to implement it in a remote technical field.

In T 1087/15 the board pointed out that knowledge of the claimed invention was absolutely necessary in order to formulate the objective technical problem, irrespective of how 'close' the prior art document was to the claimed invention; the features differentiating the claimed subject-matter from the starting document must be identified, their technical effect determined and thus the problem to be solved formulated. In as far as such knowledge of the claimed invention was labelled as 'hindsight', this particular type of hindsight was indeed a necessity in order for the technical problem to be formulated on an objective basis. As long as there was no reason (primarily a technical reason) why the content of the document selected as the closest prior art would itself not be suitable or compatible for use with respect to the subject-matter claimed, any analysis of 'how close' the prior art starting document was judged to be to the claimed invention was not something which should exclude it from being the closest prior art.