According to the case law of the boards of appeal, the person skilled in the art should be presumed to be an experienced practitioner who has average knowledge and abilities and is aware of what was common general knowledge in the relevant art concerned at a particular time (average skilled person). He should also be presumed to have had access to everything in the state of the art, in particular the documents cited in the search report, and to have had at his disposal the normal means and capacity for routine work and experimentation (Guidelines G‑VII, 3 – November 2015 version). The skilled person will be an expert in a technical field (T 641/00, OJ 2003, 352). T 39/93 (OJ 1997, 134) explained that, whilst generally accepted definitions of the notional "person skilled in the art" did not always use identical language to define the qualities of such a person, they had one thing in common, namely that none of them suggested he was possessed of any inventive capability. It was the presence of such capability in the inventor which set him apart from the notional skilled person.
With regard to the definition of the skilled person, the board in T 26/98 summarised the following principles which are generally applied by the boards of appeal: if the problem prompts the skilled person to seek its solution in another technical field, the specialist in that field is the person qualified to solve the problem. The assessment of whether the solution involves an inventive step must therefore be based on that specialist's knowledge and ability" (see crucial decision T 32/81, OJ 1982, 225; T 141/87, T 604/89, T 321/92). The skilled person can be expected to look for suggestions in neighbouring fields if the same or similar problems arise in such fields. The skilled person can be expected to look for suggestions in a general technical field if he is aware of such fields. In advanced technical fields the competent "skilled person" could be taken to be a team of experts from the relevant technical branches. Solutions to general technical problems in non‑specific (general) fields are considered to form part of the general technical knowledge.
In T 1464/05 the board considered the features made available to the public by the public prior use as the closest state of the art. The board stated that, according to established doctrine, the notional person skilled in the art referred to in Art. 56 EPC 1973 was assumed to be aware of the totality of the prior art pertinent to the relevant area of technology and in particular of everything made available to the public within the meaning of Art. 54(2) EPC 1973. The different means by which the state of the art was made available to the public ranked equally with each other. The notional skilled person was supposed to be aware of all the features of the prior use in suit that had been made available to the public. Thus, although it would be unrealistic to assume that all skilled members of the interested public would have been aware of the features made available to the public by the prior use, the notion of the skilled person under Art. 56 EPC 1973 ensured that any obvious development or application of the features of the public prior use by any particular skilled member of the interested public who had gained information on the features made available to the public by the prior use was treated under Art. 56 EPC 1973 as such, i.e. as obvious with regard to the state of the art, irrespective of whether or not other members of the interested public had actually become aware of the features of the prior use.
In T 1030/06 the application related to a system and method for securely buffering content. The board considered that the skilled person was a person of ordinary skill in the art which meant not only having access to the state of the art and common general knowledge in the field, but also the capability to perform routine work and experimentation. Thus, the skilled person could be expected to seek out solutions and make choices to try to solve design problems that crop up.
According to T 422/93 (OJ 1997, 25), when examining for inventive step using the "problem and solution approach", the starting point for defining the appropriate skilled person was the technical problem to be solved on the basis of what the prior art disclosed, irrespective of any other definition of the skilled person suggested in the contested patent. Since the technical problem addressed by an invention had to be so formulated as not to anticipate the solution, the skilled person to be considered could not be the appropriate expert in the technical field to which the proposed solution belonged if this technical field was different to the one considered when formulating the technical problem. Nor did the appropriate skilled person's basic knowledge include that of a specialist in the different technical field to which the proposed solution belonged, if the closest prior art gave no indication that the solution was to be sought in this other technical field.
In T 25/13 the board stated that opponents were essentially free to choose the starting point for assessment (here D4), but their choice then had implications for the technical knowledge of the relevant skilled person. The board concluded that there were two options: either to take the skilled person in the field of the invention (motor vehicle) – who would never have consulted D4 (tumble dryers) because it was from a totally different field – or to take D4 as the starting point, in which case the skilled person's field would be domestic appliances and the solution would not be obvious to him.