That an invention is obvious, and the patent for that invention therefore invalid, is an allegation often made in patent actions. At first glance what the inventor actually did, may illuminate the question of what was obvious at the time. For example, if it took the inventor a long time to conceive of the inventive idea, this might indicate that the invention is not obvious. Or, if the inventor conceived of the invention more-or-less straightaway, that might suggest that it is obvious.
In English legal proceedings there has long been a principle of disclosure (or discovery as it used to be known). Although the obligations have changed over the years, the basic premise has remained the same - if a party has documents relevant to an issue they must be disclosed to the other party whether they help or hinder either party's case.
Combining these two points, it was for many years the default position that a patentee should provide disclosure showing how the invention was made. This can, and does, add significantly to the costs of patent disputes in England. Given that documents disclosed in English proceedings often are used, or inform the litigants, in parallel proceedings in other jurisdictions, it is perhaps unfair to attribute all those costs just to the English action, but nevertheless it is a burden. The costs arise not just in relation to finding the documents and assessing whether they may need to be disclosed, but also the costs for the recipient in assessing those documents, and the almost inevitable satellite disputes as to whether the disclosure exercise has been done properly and thoroughly.
Over the years, therefore, steps have been taken to reduce the burden and costs of disclosure. For example, to time limit documents to those coming into existence two-years either side of the priority date, and in proceedings in the Intellectual Property & Enterprise Court (IPEC) the default position is that there is no such disclosure.
It must be stressed that these are the default positions: it is, and always has been, possible for parties to seek wider or narrower disclosure. The recent case of Positec v Husqvarna  EWHC 1061, a case relating to robotic lawnmowers, considered what should be the default position in High Court patent cases. Having first agreed that the default option should apply (i.e. that it should disclose documents that relate to validity coming into existence in the period two-years either side of the priority date), Husqvarna (the patentee) then changed its position and argued that there should be no disclosure relating to the validity of the patent. The matter came before the court at the Case Management Conference.
The Judge, Birss J., went back to basics and considered the hypothesis set out in the first paragraph above, and felt that it could be flawed for a number of reasons. First, it could only ever be an indicator of obviousness: the actual inventor may at first miss an obvious solution; or may accidently and with ease stumble on a non-obvious solution. More importantly, it misses the point that the inventor is not the "skilled person". The inventor may be, and often is, very skilled in his or her technical field and a skilled person in that sense, but that does not mean that he or she is a "skilled person" in the sense that the term is used in patent actions. The question of obviousness is considered through the eyes of a "skilled person", but the "skilled person" is not (and is very unlikely ever to be the same as) a real person. As Birss J. put it,
"The person skilled in the art is a normative legal construct and, while that notional person must have characteristics grounded in reality (see Teva v Leo  EWCA Civ 779), no real person is the same as the notional person skilled in the art. They know more but foresee less than real skilled people. They know all common general knowledge but nothing else and always read with interest even the most obscure (but public) documents. They only foresee what is obvious because, unlike real technical people, they take no inventive steps. Therefore evidence of what the inventor actually did can often be of little value and since, by definition they did make the invention, there is always a risk of hindsight. To establish that such evidence is probative can descend into a satellite dispute about how similar the inventor was to the person skilled in the art."
Birss J. went on to say,
"The reality is that in most patent cases secondary evidence, including disclosure from the patentee about what the inventor did is a costly distraction, but in a minority it can be important. This reality has been true for decades."
This case was not the first time this issue has been grappled with. The same point was made with some force in the Court of Appeal by Jacob LJ in the case Nichia v Argos  EWCA Civ 741, and he concluded that,
"I think the time has now come to hold that proportionality requires that normally such disclosure should not be ordered."
However, the other Court of Appeal Judges (Rix and Pill LJJ) with "great diffidence and reluctance" went the other way. As Rix LJ put it,
"Above all, it would be against the interests of justice if documents known to exist, or easily revealed, which would harm a party's own case or assist another party's case need not be disclosed because of a blanket prima facie rule against any standard disclosure. Once such a principle of disclosure were known to hold sway, dishonest or cavalier litigants would reap an unmerited advantage, contrary to the interests of justice."
Thus, the position remained unchanged - i.e. normally such disclosure should be ordered.
Given the changes to the Civil Procedure Rules since the Court of Appeal Judgment in Nichia v Argos, Birss J. did not feel bound by it, but he still had to grapple with the balance between encouraging cost-effective and proportionate patent litigation in the English jurisdiction, with English principles of fairness that a party should not be able to keep salient materials from their opponent or the court. However, as Birss J. mentions, the fact is that in IPEC such disclosure is not normally ordered, and there is no suggestion that fairness does not apply. (In contrast, in other jurisdictions fairness is viewed differently; for example in Germany the attitude to disclosure in civil matters is akin to that in criminal matters, i.e. self-incrimination is unfair.)
Proportionality is a question of balancing the costs of a disclosure exercise with the value of the claim, and the likely probative value of any documents that might be disclosed. Birss J. considered that both sides' costs for the claim as a whole (although higher than desirable) were not out of kilter with the value of the dispute. He also concluded that the costs of a disclosure exercise were not a very substantial aspect of the overall costs. The costs of disclosure were not, therefore, disproportionate to the value of the claim. However, Birss J. concluded that the costs would be disproportionate to the likely probative value of the documents disclosed, and therefore he would not order disclosure of the patentee's documents relating to validity.
Unless the documents are somehow nevertheless revealed, we will never know what probative value they may have had, and whether Birss J. was right in his conclusion that they were unlikely to have much, if any value, but in all likelihood Birss J. is correct in this view, as historically it has only ever been in a minority of cases that such documents have made a material difference. By this decision, Birss J. has reset the default position: in English proceedings in which the validity of the patent on the basis of obviousness is in issue, ordinarily the patentee will not be ordered to disclose documents relating to the making of the invention.
This brings the English patent procedure in the High Court into line with IPEC and the expected practice at the looming Unified Patent Court ("UPC"). As Birss J. was previously the Judge at IPEC and has seen the benefits of limiting disclosure first-hand, his decision is perhaps unsurprising. One can further speculate that Birss' decision was influenced by a desire to keep English patent litigation in line with, and a competitive alternative to, the UPC for national patents or opted-out European patents.