http://ipkitten.blogspot.com/2022/11/burden-of-proof-for-inventive-step.html
The recent decision T 0555/18 from the EPO Boards of Appeal considered the burden of proof for unusual parameters relied on for inventive step. The patent in question (EP2117839) related to shrink wrap for use in food packaging. On appeal, the Opponent argued that the patent lacked inventive step. The only distinguishing feature between the prior art and the claimed invention was found to be the specified range of an unusual parameter that was not commonly used in the field of shrink wrap. The question before the Board of Appeal thus became whether the unusual parameter could be relied on for inventive step.
Legal background: Unusual Parameters
| Shrink wrap |
“Unusual parameters” are those which are not commonly used in the technical field of an invention (F-IV, 4.11.1). When specified in a patent claim, unusual parameters can only confer novelty on the invention when the parameter can be easily measured or converted to a normal parameter. In other words, it must be straightforward for a skilled person to assess whether the parameter corresponds to a true distinguishing feature of the invention from the prior art. Furthermore, the burden of proof is placed on the Patentee to show that an unusual parameter relied on for novelty does actually distinguish the claimed subject-matter from the prior art (Case Law of the Boards of Appeal, III-G, 5.2.2(d), T 0131/03, T 2732/16).
Case background
In T 0555/18, the Patentee submitted that the claimed invention solved the problem of providing a shrink wrap film that was sufficiently strong without compromising on transparency. The granted claims specified shrink wrap films having a “FTIR Transmission Absorbance Ratio” (FTIT ratio) of 1.65 or lower. The patent explained in the description that a low FTIT ratio value implied a film with a large polyamide content (i.e. high strength) and a low degree of crystallinity (i.e. transparency).
The Board of Appeal considered the FTIT ratio to be an unusual parameter not commonly used in the field (r. 1.5.5). The specified FTIT ratio range was also found to be the only distinguishing feature between the claimed film and the films disclosed in the closet prior art (r. 1.3). The question became whether it would have been obvious for a skilled person to make films having FTIT ratios falling within the claimed range.
Reliance on an unusual parameter for inventive step
The Board of Appeal noted that the very unusualness of an unusual parameter might cloud the issue of obviousness. A rare parameter might appear to confer distinctiveness on an invention that is, in fact, inherently lacking. Furthermore, substituting a more common parameter to indirectly compare the invention to the prior art might itself lead to uncertain conclusions. In such cases, the Board of Appeal thought it appropriate to follow the case law on unusual parameters in the context of novelty (T 0131/03, T 2732/16). In other words, the burden of proof should lie with the Patentee to demonstrate that obvious solutions in view of the prior art would not implicitly fall under the scope of the unusual parametrical range specified by the claim (r. 1.6.1).
In the case in question, the Board of Appeal found that the obvious solutions that would suggest themselves to the skilled person in view of the prior art would necessarily result in films having the FTIT ratios falling within the scope of the claimed invention. The burden of proof was then placed on the Patentee to demonstrate that this would not be the case. The fact there was no definitive proof either way as to whether the obvious solutions would fall under the scope of the claims appeared to the Board of Appeal “to be an attempt by the proprietor to benefit from the uncertainties caused by its decision to draft the invention in terms of an unusual parameter, which is precisely what the board intends to avoid by shifting the burden of proof to the proprietor or by giving the opponent the benefit of the doubt.”
In the absence of proof establishing that the obvious solutions in view of the prior art would not fall under the scope of the claim, the claims were found to lack inventive step.
Final Thoughts
The decision of the Boards of Appeal in this case flows naturally from the requirement in Europe that the technical effects of a claimed invention and that of the closet prior art to be directly compared. The decision in T 0555/18 is a caution against defining an invention by unusual parameters that make it difficult to compare the technical effect of the invention with that of the prior art. When including any parameter in a patent application, it is therefore critical for the skilled person to be able to straightforwardly measure that parameter, both when practising the invention and for prior art disclosures.
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