T 0131/03 vom 22.12.2004

In inter-partes proceedings the burden of proof rests primarily upon the opponent. However, when the latter has established a strong presumption that unusual parameters as used to define the claimed subject-matter are inherently disclosed in the prior art, the patent proprietor cannot merely claim the benefit of the doubt. It is incumbent upon him to contribute in establishing to which extent such parameters, which he freely chose to use in the definition of his invention, actually distinguish the claimed subject-matter from the prior art (points 2.3 to 2.8 of the Reasons).