IP-2024-000061 - [2025] EWHC 1936 (IPEC)

A classic description of persons skilled in the art was given by Lord Diplock in Catnic Components Limited v Hill & Smith Limited [1982] RPC 183, at 242, namely:

Lord Diplock’s characterisation may sometimes be unsatisfactory when considering inventive step. The assumption that the skilled team has a practical interest in the subject-matter of the invention can, on certain facts, broaden the scope of CGK held by the team in a manner which unfairly prejudices the patentee.

This was not a point that the House of Lords had to consider in Catnic. In Schlumberger Holdings Ltd v Electromagnetic Geoservices AS [2010] EWCA Civ 819, Jacob LJ pointed out that Catnic was concerned with the scope of the claims in suit, not inventive step (at [38]).

The potential unfairness to the patentee arises where the invention claimed relates to a problem which existed in a first technical field at the priority date; the patentee says that the problem is solved by the application of a concept drawn from a second, technically remote field. Technically remote here means that the CGK of a skilled person the first field does not closely overlap the CGK of a skilled person from the second field – the more remote the fields, the less overlap there will be.

Those were the facts in Schlumberger. The Court of Appeal ruled that in consequence the composition of the skilled team through whose eyes inventive step was to be assessed should be different from the composition of the skilled team assessing, for instance, insufficiency, where the team’s knowledge of the invention is required, see Schlumberger at [22] to [70].

Jacob LJ went on to explain how inventive step must be approached in such circumstances:

When Jacob LJ said at [72] that the problem ‘must’ also be approached the other way around, presumably he meant that one or other, or optionally both analyses must be adopted.

So in a case like Schlumberger the first possibility is that inventive step falls to be assessed from the perspective of the skilled team drawn from the field of the problem: at the priority date would such a team have contemplated solving the problem by using the relevant concept drawn from the remote field of the solution? Alternatively, would the relevant concept been seen by the team as having a sufficient prospect of being useful that an expert in the field of the solution should be consulted?

The second possibility is that inventive step is assessed from the perspective of a skilled team from the field of the solution. At the priority date would a skilled team from the field of the solution have contemplated applying the relevant concept used in that field to a project in the field of the problem, specifically to solve the problem in question? Or at least would it have been considered worthwhile to consult a person with expertise from the field of the problem?

If the answer to either question is yes, the invention is likely to lack inventive step. If the answer to both is no, there is an inventive step.

This is jumping ahead to inventive step. The more immediate point is that in a case like Schlumberger, for the purpose of assessing inventive step the skilled team may come from either the field of the problem or the field from which the concept of the solution is drawn. Either way, it is not a Catnic team.

In most instances the Catnic formulation works perfectly well and identifies the same skilled person or team for all purposes, see Schlumberger at [40] and Medimmune Ltd v Novartis Pharmaceuticals UK Ltd [2012] EWCA Civ 1234, at [72]. A Catnic team makes life simpler, but where there is doubt that such a team is appropriate for inventive step, the Schlumberger approach is to be taken.

In Illumina Cambridge Limited v Latvia MGI Tech Sia [2021] EWHC 1026 (Pat) Birss J proposed the following steps in such a case (at [68]):

As indicated in Schlumberger, there is also nothing wrong with considering instead the established field from which the solution to the problem is taken and assessing inventive step from the perspective of a person or team in that field, although this may require the citation of different prior art. Or both can be done as alternatives.

The reference in Illumina to an ‘established’ field is a reminder of a related principle of law: any field of problem team or field of solution team must come from a technical field known to have existed at the priority date, see Schlumberger at [42] and Medimmune at [76]. Neither may be from a technical field which did not then exist.

Taking the example of beginning with a field of problem team, such a starting team is to be identified as described in Illumina. It is a starting team because that is not necessarily the end of the process for identifying the final hypothetical skilled team.

It is to be expected in such a case that cited prior art will come from the field of the solution. As Jacob LJ indicated in Schlumberger, the team from the field of the problem is deemed to have read each cited item of prior art and the court must decide whether such a team would then either have (a) perceived the invention or (b) decided that the concept disclosed in the prior art had a sufficient prospect of being useful such that it was worth consulting an expert in the field from which it was drawn.

The hypothesis is that the skilled team will read each item of cited prior art with care and interest, no matter how remote the field from which comes. If (b) is applicable, the skilled team may expand to include an expert from the second field. This could be viewed as the original team consulting someone else without formally expanding the team. It makes no difference – in effect, there is an expanded team which will probably no longer collectively come from an established field.

There is a procedural aspect to this. In such a case the evidence presented at trial will have to be prepared in successive stages. First, there will be evidence from an expert from the field of the problem. Without knowledge of the patent in suit but with access to the cited prior art, that expert must initially consider whether a skilled person from the field of the problem, having read the prior art with care and interest, would either have contemplated the invention or alternatively would have taken the view that the prior art discloses information which has a sufficient prospect of being useful that it would have been worthwhile consulting someone from the field of the prior art, i.e. the field of the solution. The expert’s evidence on this is of course recorded. If it is his or her belief that the skilled person would have thought it worthwhile to consult someone from the field of the prior art, an expert from this second field will then discuss the matter with the first expert. Preparation of evidence from the experts on the likely views of the combined hypothetical skilled team will subsequently go forward in the usual way.

If the foregoing procedure is adopted, expert evidence as to whether the starting skilled person or team would have consulted someone from outside their established field ought not to be vulnerable to hindsight. Even so, such evidence and the reasons given in support of it will be considered with appropriate care.

Thus, for the purpose of assessing inventive step, there may be a Catnic team, or alternatively the assessment starts with a field of problem team or a field of solution team. Usually, a Catnic team will be suited to the task and it will be more efficient for all concerned if that single team is used for inventive step and anything else that falls to be considered by the skilled team. Occasionally, a field of problem team or a field of solution team will be required as the starting team for inventive step. In principle both could be used, subject to the permission of the court.

A party seeking to rely on a field of problem team or a field of solution team should plead their case accordingly, This will give the opposing party the opportunity to file evidence to deal with that approach at the trial, or alternatively to challenge the approach if it is appropriate to do so. The pleading will also provide justification (particularly in this court) for each side to seek to call more than one expert.