5. "Could-would approach" (obviousness)

To determine whether the claimed invention, starting from the closest prior art and the objective technical problem, would have been obvious to the skilled person, the boards apply the "could-would approach" (see also EPC Guidelines G‑VII, 5.3 – April 2025 version). This means asking not whether the skilled person could have carried out the invention, but whether they would have done so in the expectation of solving the underlying technical problem or in the expectation of some improvement or advantage (T 2/83, OJ 1984, 265; T 90/84; T 7/86, OJ 1988, 381; T 200/94, T 885/97, T 1148/15). When considering whether or not claimed subject-matter constitutes an obvious solution to an objective technical problem, the question to be answered is whether or not the skilled person, in the expectation of solving the problem, would have modified the teaching in the closest prior art document in the light of other teachings in the prior art so as to arrive at the claimed invention (T 1014/07, T 867/13). The answer to this question depends on the result the skilled person wished to obtain (T 939/92, OJ  1996, 309; see also e.g. T 1249/20). The point is thus not whether the skilled person could have arrived at the invention by modifying the prior art, but rather whether, in expectation of the advantages actually achieved (i.e. in the light of the technical problem addressed), they would have done so because of promptings in the prior art (T 219/87, T 455/94, T 414/98, T 2197/19).

In T 1014/07 the board stated that since this question involved determining whether or not the skilled person would – and not could – have made a particular modification, it was necessary for answering the question to identify conclusive reasons on the basis of tangible evidence that would have prompted the skilled person to act in one way or the other. The board in T 1045/12 found that its decision, being based on prior art documents D4 and D3, was based on "tangible evidence" (referring to T 1014/07).

It has been held that once an invention existed, it could often be shown that the skilled person could have made it by combining different elements in the prior art, but such arguments had to be disregarded as the product of ex post facto analysis (T 564/89).

According to T 939/92 (OJ 1996, 309), the answer to the question what a skilled person would have done depended in large measure on the technical result they had set out to achieve. In other words, the notional "person skilled in the art" was assumed to act not out of idle curiosity but rather with a specific technical purpose in mind (see also T 28/20, T 2029/21).

In T 2197/11 the board held that the selection of a potentially less advantageous size-reduced L-carnitine acid fumarate did not require inventive ingenuity, if, as in the present case, it merely amounted to tolerating clearly predictable disadvantages. It belonged to the routine work of a person skilled in the art to decide under the given circumstances whether the potential advantage outweighed potential disadvantages and which of the potential disadvantages were acceptable. Inventive skills are not required in this respect.

In T 867/13 the board pointed out that what the skilled person, starting from the closest prior art and faced with the objective technical problem, would or would not do depends not solely on the disclosure of the closest prior art document, but also on the state of the art in the relevant technical field (see also T 3016/18).

In T 1126/09 the board pointed out that, in accordance with the "could-would" approach, the assessment of inventive step must involve establishing, in each individual case, to what extent the skilled person had good reason, in the light of the closest state of the art or the objective problem derivable from it, to adduce further prior art and apply its teaching to the process/apparatus of the closest prior art – or, in other words, whether any factor is discernible which points towards a combination of the teachings of the citations addressed.

Technical feasibility and the absence of obstacles were only necessary requirements for reproducibility but were not sufficient to render obvious what was actually achievable for the skilled person (T 61/90). The fact that the inherent properties of a technical means were known to the skilled person, so that they had the intellectual possibility to apply this means in a conventional device, merely established the possibility of using such technical means in such a manner, i.e. that the skilled person could have used it. However, if it was to be established that such intellectual possibility was also a technical measure which it was obvious for the skilled person to use, it was necessary to show that there was a recognisable pointer in the state of the art to combine the known means and conventional device for achieving the intended technical aim, i.e. that the skilled person would have made such a combination. The existence of such a technical reason was dependent on the known properties not only of the means but also of those of the device (T 203/93, T 280/95). That it was theoretically possible for the skilled person to arrive at the invention simply means that they could have used the requisite technical means. If, however, it was to be established that the skilled person would actually have used them, it must be possible to ascertain a pointer in the prior art which would have prompted them to do so (T 1317/08).

In T 905/17 the board did not find persuasive the opposition division's dismissal of a line of argument on the basis that there was no "hint in document D4 to suppress the liner (3) and then to search for appropriate material in the prior [sic] for the pressure armours (5,6) then subjected to corrosion". The skilled person starting from one element of the state of the art and faced with the need to solve a given problem did not necessarily need a "hint" associated with that element. Otherwise, it would never be possible to establish a lack of inventive step based on the object of a public prior use, which usually does not come with any hints. In the absence of a hint, the skilled person might still take the steps leading to the claimed subject-matter on the basis of their common general knowledge or documents belonging to the state of the art that explicitly teach a solution to the problem to be solved.

In T 555/18 the board observed that when the only feature distinguishing the invention from the closest prior art was a range of an unusual parameter, the assessment of obviousness might be clouded by the fact that such parameters were by definition rarely described in the relevant prior art. The board concluded that in such circumstances a similar approach to that proposed in T 131/03 and T 740/01 should be applied to decide on the question of obviousness. In particular, once it had been established that it would be obvious for the skilled person to solve the underlying technical problem in ways that could be presumed to inherently lead to values within or close to the claimed range, it was the proprietor who should carry the burden of proof to demonstrate that implementing such solutions would not lead to the claimed parametrical range. For more on the reversal of the burden of proof with regard to unusual parameters see chapter III.G.5.2.2d).

In T 894/19 the board noted that in cases such as the case in hand, whereby the configuration of features represented a mere obvious and consequently non-inventive selection among a number of known and equally likely possibilities, the "could-would approach" normally did not apply (see also T 1968/08, T 12/07). It held that to consider all of the solutions that were equally obvious, it was sufficient that the skilled person could recognise the solutions concerned without inventive efforts: a separate pointer was then not required for this purpose.

In T 3255/19 the board held that the person skilled in the art had no reasonable expectation of success that replacement of the asparaginase of document D8 by an asparaginase from Erwinia chrysanthemi having 90% identity to the amino acid sequence of SEQ ID NO:1 would yield a therapeutically active conjugate. The appellant's argument to the contrary did not take account of the unpredictability of the activity of the enzyme after pegylation.

In T 1231/20 the board held that once a convincing argument had been made why the claimed invention would have been obvious to the skilled person, i.e. an obvious solution to an objective technical problem which could be assumed to have arisen, the identification of a different, more specific ("subjective") technical problem as a solution to which the claimed invention might not appear to be obvious did not suffice to invalidate the finding of obviousness.

In T 149/22 the claimed invention foresaw the adding of phospholipase A to a cake batter to lower the amount of fat while preserving the resulting cake’s properties. The board found that the arguments the skilled person would have arrived at the claimed solution without the need for an inventive step were based on cherry-picking and an oversimplified interpretation of the information presented in the cited documents. The ingredients of the batter could not be expected to have the same properties and be interchangeable; if a different enzyme were included in the batter, the complexity of the resulting system did not allow any reasonable prediction to be made on the properties of the obtained product. The opponent's arguments were thus tainted by hindsight.

In T 1383/21 the board confirmed that a plurality of different features did not constitute inventive step if each feature was obvious in its own right even though each feature contributed independently of the others to solving the same problem (in this case making the apparatus more effective).