T 254/86 (OJ 1989, 115) described the objectively closest prior art as the "most promising springboard” towards the invention which was available to the skilled person (see also T 282/90, T 70/95, T 644/97).
According to T 870/96, when trying to evaluate a skilled person's capabilities and behaviour in the problem and solution approach, as closest prior art a "bridgehead" position should be selected, which said skilled person would have realistically taken under the "circumstances" of the claimed invention insofar as these circumstances can be retrieved in one item of the prior art. Consequently, among these "circumstances", aspects such as the designation of the subject matter of the invention, the formulation of the original problem and the intended use and the effects to be obtained should generally be given more weight than the maximum number of identical technical features (see also T 66/97).
In T 824/05 the board was faced with the situation of two alternative starting points equally suitable for the assessment of inventive step, whereby one starting point, i.e. D11, lead to the conclusion that the claimed subject-matter was obvious and the other starting point, i.e. D1, gave exactly the opposite result. The board held that in this situation D1 did not qualify as the closest state of the art because it did not represent the most promising springboard towards the invention.
In T 53/08, documents (1) and (10) - like the patent in suit - concerned herbicides for use in controlling weeds harmful to maize, rice and cereal cultures. Document (1) described the formula (A1) herbicide and its combination with other active ingredients, whereas document (10) disclosed compositions containing substituted isoxazoline derivatives which acted as safeners. The board found that the disclosure in each of the two documents differed from the patent in suit in respect of just a single feature. In deciding whether document (1) or document (10) had to be regarded as the closest prior art, it considered the patent's objective, which was to develop the highly effective herbicidal ingredient of formula (A1) in such a way that it did not significantly damage crops when used in a concentration with herbicidal effect. The natural starting point for the invention was therefore the document disclosing the active ingredient of formula (A1).