In a few cases, the board stated that there have been cases where inventive step was denied by the boards of appeal because the skilled person was in a "try and see" situation. Such a situation was considered to have occurred if the skilled person, in view of the teaching in the prior art, had already clearly envisaged a group of compounds or a compound and then determined by routine tests whether such compound/s had the desired effect (T 889/02, T 542/03, T 1241/03, T 1599/06, T 1364/08).
In T 1396/06 the board stated that a skilled person, even when applying routine methods with the aim of solving a closely related technical problem, would not have the absolute certainty of succeeding. However, certainty of success is not required according to the jurisprudence of the boards of appeal, which makes a clear distinction between reasonable expectation of success and certainty of success (T 918/01). Rather, in spite of the understandable uncertainties which always characterise biological experiments, the skilled person would have had no reason to adopt a sceptical attitude. He would have had either some expectations of success or, at worst, no particular expectations of any sort, but only a "try and see" attitude, which does not equate with an absence of a reasonable expectation of success (see also T 759/03).
In T 293/07 the board stated that the testing of humans could not be considered to represent known routine tests and accordingly the skilled person was not in a "try and see" situation. In T 847/07 the board considered it questionable whether the skilled person would adopt a "try and see" attitude at all in cases where human testing would be necessary in order to determine whether or not a compound has a certain property (see also T 1545/08).
In T 1545/08 the appellant asserted that the skilled person would have at least adopted a "try and see" attitude towards the use of interferon and ribavirin for treating naïve patients having an HCV 1 genotype infection, a viral load of greater than 2 million copies per ml of serum for a period of 40 to 50 weeks and hence an inventive step was not present. The board, however, stated that neither cell culture nor animal models of HCV were available one year before the priority date of the patent. In fact document (OD2) stated that "[u]nfortunately, cell culture systems and animal models of HCV replication were yet to be developed and the lack of simple in vitro and in vivo systems for evaluating antiviral agents for effects on HCV replication made it necessary to investigate agents of promise in humans with this disease." No evidence was before the board that at the priority date this situation had changed. It followed that the effect of the combination had to be tested in humans. In line with established case law the board concluded that the skilled person was not in a "try and see" situation.
In the light of the closest prior art the board saw the technical problem to be solved in T 886/91 in the exact identification and characterisation of DNA sequences of HVB genome subtype adyw. The board pointed out that the situation in T 886/91 could not be compared with the one in T 223/92 and T 500/91, where production of a partially known protein in a recombinant-DNA system was achieved and considered inventive on the basis of the fact that, in the specific circumstances of those cases, there was no realistic expectation of success. In the case in point the closest prior art had already disclosed the cloning and expression of the HBV genome subtype adyw. The identification and characterisation of the claimed specific sequences of the same genome involved for the skilled person nothing more than the performance of experimental work by routine means in connection with the normal practice of filling gaps in knowledge by the application of existing knowledge.