Patent Litigation in Practice Series: Spotlight on the UK: The use of experts

“...incapable of scintilla of invention… also very forgetful… an assembly of nerds of different basic skills, all unimaginative” but “not a complete android” (Technip France SA’s Patent [2004] EWCA Civ 381).  

A template for a good online dating profile, this is not.  Instead, these are the essential characteristics of the notional skilled addressee of a patent in the UK. It is through the eyes of this skilled person (or skilled team) that the UK courts must approach many of the key facets of patentability, from claim construction through to obviousness.  

The UK courts are not unique in relying on expert evidence in order to help understand how the skilled person would have understood certain concepts at a relevant date. Yet it is perhaps the approach for how these experts are instructed and deployed that, to those on the outside, might seem strange.  Let us look into this in a bit more detail.

Role of an expert in the UK

The primary function of an expert is to educate the court in the technology of the patent. Throughout their role, the expert owes an overriding duty to the court and not to the party instructing them (see Civil Procedure Rules (‘CPR’), Part 35). Their evidence will usually take the form of a written report, plus one or more reports submitted in reply to the evidence of the opposing party.  An expert may (but not always) give further oral evidence by way of cross-examination during trial. This evidence must be independent, unbiased, uninfluenced by the pressures of litigation and the expert should not assume the role of an advocate (Practice Direction to CPR35).  

Preparation of the expert’s report

There is an onus on the instructing solicitors to help ensure that their expert is able to meet their duties under the CPR.  In recent years there has been a particular focus on how expert evidence is prepared in patent cases and the sequence in which experts are shown documents (Fisher & Paykel v Flexicare [2020] EWHC 3282 (Pat)). 

In short, judges’  preferred approach is:

1. First ask the expert about the common general knowledge (‘CGK’) relating to their field; 
   
2. Next,  show the expert the relevant prior art and to ask them questions such as what steps would be obvious to take in light of the document(s); and 
   
3. Only then, to show the expert the patent-in-suit.  

This approach is often referred to as “sequential unmasking” (Akebia v Fibrogen [2020] EWHC 866 (Pat)).  The aim is to try to mitigate hindsight creeping into the expert’s analysis of what would be obvious (or non-obvious) to try.  If an expert has seen the patent before discussing the CGK or the prior art, their opponent  may argue that their view on, for example obviousness, always had a particular end-point in mind and, therefore, is no longer free from bias.  

Although a preferred approach, this is not an absolute requirement by the UK courts. There may be occasions where new prior art comes to…