The life of a patent attorney is hard enough as it is, but using the EPO claim drafting convention, one would be forgiven for thinking that after carefully steering around the prior art in the ‘pre-characterising’ portion of the claim, that would be enough. Not so.
In the recent Court of Appeal decision of Lufthansa Technik AG v Astronics Advanced Electronics Systems and ors  EWCA Civ 20 the distinction fell to be considered. In the judgement of LJ Birss, he said:
This case highlights a curiosity of the pre/post characterising approach to claim drafting. When drafted this way the characterising features of the claim explain what the patentee thought were features not disclosed in the prior art on which the pre-characterising part was based….. In other words these characterising features are presented as representing the inventive step over that prior art. However the challengers to validity in this case, as they are entitled to, rely on different prior art. In response the patentee seeks to identify distinctions over that other prior art. As it turns out in this case those distinctions are features of the pre-characterising part. So the inventive step (if it is one) over the other prior art may very well not be the features in the characterising portion of the claim at all. I mention this only to make the point that it is a legitimate approach for patentees to take. Many good inventions amount to new combinations of old features. The fact that each of the individual features making up a claimed invention can be found in various places in the prior art may well help the party challenging validity to make their case but it does not, on its own, prove that a claim lacks an inventive step.
The case concerned plug sockets in aircraft seats. The patent’s invention lay in the socket detecting a plug’s insertion, and that the power supply was ‘remote’ from the socket. The arguments revolved around whether there was a need for full insertion or only partial insertion, and what was understood by ‘remote’. If the claim was construed (normally and purposively – there was no equivalence issue) so that only partial insertion was required, then a piece of prior art (not that which the pre-characterising portion related to) was engaged.
At first instance, the judge concluded that the claims required full insertion, and that ‘remotely’ for the power supply meant well away from and not simply in close approximation to the socket. The patent was held to be valid and infringed.
Despite the apparent change of tack by the appellants in citing different prior art (the case also considered whether there should be permission to amend, but either way, the prior art arguments had to be considered); they were no more successful than they were below. One of the specific grounds for appeal was that the judge had used the drawing reference numerals in order to construe the claim: impermissible following the Virgin Atlantic v Premium Aircraft  EWCA Civ 1062. The appeal failed, not least because, contrary to the appellants view, the judge had considered not only Virgin Atlantic and how reference numerals were to be considered but also noting Adaptive Signal and Spectrum Alignment Inc v BT  EWCA Civ 1462, that claims can be either narrower or wider than specific embodiments. The judge’s approach was considered to be ‘entirely orthodox’ and upheld on appeal on all the issues arising.
Although a somewhat rare and extreme case, it nevertheless highlights the need for caution in both drafting around prior art provided by the inventor/applicant and giving validity opinions on the same.