c) Art. 84 and 123(2) EPC – inescapable trap 

In T 81/13 the board refused claim 1 of the main request as it contained a viscosity feature which the board considered not clear (Art. 84 EPC). In claim 1 of the auxiliary request the appellant deleted this viscosity feature and argued that an unclear and unmeasurable viscosity value was not essential and could be omitted for this reason from the claim; this omission should also be possible to escape the Art. 84 and 123(2) EPC "squeeze", which would lead to an "inescapable trap". The board held that this parameter was revealed to be unclear but remained an essential feature since, even unclear, it conferred on the composition a particular aspect and reflected a composition having specific and essential properties. Also, the presence of an unclear essential feature in a claim did not inevitably lead to an "inescapable trap". If the omission of such feature reflecting essential properties of a claimed product was not possible, its replacement by an equivalent feature providing inevitably the same essential property could be considered as normally feasible. This was usually possible through the incorporation of adequate technical features able to provide inevitably said property. As a last resort, the claimed subject-matter could even have taken the form of an exemplified subject-matter. In the case at issue, the application as originally filed presented a disclosure deficiency and if there was an inescapable trap, it was rather linked to this deficiency.

T 1420/15 is an example of a case in which the patent proprietor could not escape the trap, as the unclear feature contained in claim 16 as filed, but omitted in the claim as granted, provided a technical contribution by excluding certain types of pet food compositions.

The case law on the "inescapable trap" between the requirements of Art. 123(2) EPC and Art. 123(3) EPC is reported in chapter II.E.3.