3.2. Approaches to selecting the closest prior art

According to the board in T 24/81 (OJ 1983, 133), the closest prior art must be assessed from the skilled person's point of view on the day before the filing or priority date valid for the claimed invention (see T 772/94; T 971/95; see also EPC Guidelines G‑VII, 5.1 – April 2025 version).

In T 1212/01 the board held that the determination of the closest prior art was an objective and not a subjective exercise. It was made on the basis of the notional skilled person's objective comparison of the subject-matter, objectives and features of the various items of prior art leading to the identification of one such item as the closest.

In T 2759/17, however, the board highlighted two different approaches in the case law with regard to the choice of starting point. In a first approach, it is the deciding body that selects the closest prior art (see e.g. T 1241/18, T 1450/16, T 855/15). In a second approach, the skilled person comes into play as early as when the closest prior-art disclosure is being selected (see also e.g. T 254/86, T 2148/14).

The board in T 1450/16 did not agree that, according to the basic problem-solution approach, the person skilled in the art may be entrusted with the task of selecting the closest prior art or a suitable starting point for the assessment of inventive step. This would mean that the same (fictitious) person who assesses the obviousness of a certain claimed subject-matter would have already selected their "favourite" prior art document in order to conduct that assessment, which would further imply that this skilled person could pose the objective problem to themselves. This would, according to the board, be at odds with the aim of the problem-solution approach to provide an objective method of evaluating inventiveness, avoiding as far as possible an inadmissible hindsight analysis. The board, following the conclusions drawn in T 422/93, thus expressed the view that the person skilled in the art within the meaning of Art. 56 EPC entered the stage only when the objective technical problem had been formulated in view of the selected "closest prior art". Only then could the notional skilled person's relevant technical field and its extent be appropriately defined (see chapter I.D.8.1). Therefore, it could not be the "skilled person" who selected the closest prior art in the first step of the problem-solution approach. Rather, this selection was to be made by the relevant deciding body (whose members could not be equated with the skilled person as a notional entity: T 1462/14; see also chapter I.D.8.1.1), on the basis of the established criteria, in order to avoid any hindsight analysis.

In T 154/17 the board confirmed the selection of a starting point served the purpose of assessing inventive step and was thus not selected by the person skilled in the art, but by the body deciding on inventive step, from among the prior-art disclosures that were eligible under Art. 56 EPC. The notional person skilled in the art entered the scenario of the problem-solution approach only after the objective technical problem had been determined. What teaching the skilled person or team seeking to solve the objective technical problem would have derived from the starting point and any supplementary prior-art disclosures, must then be assessed from their point of view before the effective date. In this way, obviousness is assessed without hindsight.

The board in T 2759/17 observed with regard to the first approach, in which the deciding body selects the closest prior art, that the skilled person and their expectations, prejudices, knowledge and abilities did not play any role in the selection, but came into play later on when the closest teaching had been identified and the problem formulated. It would not be possible under this approach to disregard a technical teaching on the ground that the skilled person would not have considered it to be the most promising – or at least an otherwise realistic – starting point. In the second approach identified by the board, the technical teaching from which the skilled person would have realistically started as the most promising springboard towards the invention therefore needed to be determined (see e.g. T 254/86, T 2148/14). Under this approach, the skilled person was held to generally look for a disclosure that aimed at a purpose or effect that was the same as or at least similar to the one underlying the patent in question (see e.g. T 710/97). Following this approach, it was possible to reject an inventive-step attack on the ground that the skilled person would not have realistically selected the specific disclosure on which the attack in hand relied as a starting point (see e.g. T 1307/12, T 2114/16).

It was the board’s firm conviction in T 2759/17 that, in line with the established case law, the skilled person was the relevant point of reference right from the start of any inventive-step assessment. Determining whether an invention was inventive involved technical considerations, and those had to be made through the eyes of the skilled person. Excluding the skilled person for part of the inventive-step assessment would lead to artificial and thus technically meaningless results. Under this premise, at least in the field of chemistry, with which the case in hand was concerned, the skilled person normally did not arbitrarily pick any existing prior-art disclosure and only then start to think about the technical field in which it might be applied and what effect it could possibly achieve. The board found that unlike the first approach, the second approach was based on a technically meaningful and thus realistic scenario. More specifically, the skilled person was normally confronted with a certain purpose or effect to be achieved in a certain technical field. With this in mind, the skilled person would then look for a prior-art disclosure that was in the same technical field and aimed at the same or a similar purpose or effect. This, in the board's view, was what was meant by the "most promising springboard" (see chapter I.D.3.7.2). Applying this second approach thus avoided the drawback of using hindsight when selecting the starting point for assessing inventive step.

Further decisions in which the boards of appeal at least implicitly indicate that the skilled person may select the closest prior art include T 1841/11, T 2057/12, T 1248/13.

See also chapter I.D.8.1.2 "Point at which the skilled person enters the stage"