d) Unusual parameters 

In T 131/03 the board pointed out that, once the opponent had established a strong presumption that unusual parameters as those used to define the claimed subject-matter were inherently disclosed in the prior art, the patent proprietor could not merely claim the benefit of the doubt. It was incumbent upon the patentee to establish the extent to which the parameters used in the definition of its invention actually distinguished the claimed subject-matter from the prior art (followed by T 2732/16). See also T 1452/16 (unusual parameters – alleged prior use – public availability of a product): as to the possibility for the patent proprietor to obtain samples and test them, the board stated that when testing samples manufactured after the priority date the legitimate question could arise of whether the results obtained were representative of the ratios present in the samples of the prior art. However, by using a parameter which had not been used in the prior art, the burden was on the patentee to prove that the prior art did not fall within the terms of the claim.

In T 1666/16 the appellant (opponent), relying on T 131/03 and T 740/01, argued that since the angle of repose (PVDF resin powder) was an unusual parameter in the context of PVDF resins, it would be legitimate to reverse the burden of proof and require the patent proprietor, who had chosen to rely on an unusual parameter as the sole distinguishing feature over the powder disclosed in example 4 of D1, to demonstrate that this parameter was not fulfilled by that powder in D1. The board decided that T 131/03 and T 740/01 were based on the same rationale, namely that when it had been established that there was a strong presumption that claimed subject-matter defined by an unusual parameter was inherently disclosed in the prior art, the patent proprietor could not merely claim the benefit of the doubt and had to demonstrate that the chosen parameter-based definition distinguished the claimed subject-matter from the prior art. In T 1666/16, however, the appellant had failed to show that the unusual parameter was inherently disclosed in the prior art and there was therefore no justification for reversing the burden of proof.

In case T 555/18, contrary to the proprietor's view, the FTIR ratio was considered to be an unusual parameter and consequently, in case of doubt it was the proprietor who carried the burden of proof to demonstrate that working within the defined range would not be obvious in view of the cited prior art. The board stated that the concept of "unusual parameter" did not necessarily imply that the parameter was unknown, but rather that it was uncommon in the sense that it was not generally used in the specific form proposed in the claims within the underlying technical field. The board then 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 (concerning novelty) 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 (See Catchword). The board considered that it would be unequitable for a party to benefit from the uncertainties created by its decision to define the invention in terms of an unusual parameter, which was precisely what the board intended to avoid by shifting the burden of proof to the proprietor or by giving the opponent the benefit of the doubt.

In T 2037/22 the appellant (opponent) argued that in view of the unusual parameter of the patent, it would be legitimate to reverse the burden of proof and to require from the respondent, having chosen to rely on an unusual parameter as the sole distinguishing feature over the compositions disclosed in D6 and D7, that it demonstrate that this parameter was not fulfilled by these compositions. The appellant relied in support of its case on decisions T 131/03, T 740/01, T 2732/16 and T 1666/16. The board stressed that all these decisions were based on the same rationale, namely that when a strong presumption has been established that a claimed subject-matter defined with an unusual parameter is inherently disclosed in the prior art, the patent proprietor cannot merely claim the benefit of the doubt and has to demonstrate that the parametric definition chosen distinguishes the claimed subject-matter from the prior art. The appellant had not succeeded in showing that it was reasonable to assume that a variation of b-value of less than 2 was inherently achieved by the compositions of D6 and D7. Accordingly, there was in the present case no justification to reverse the burden of proof. The subject-matter of operative claim 1 was novel over each of D6 and D7.