In Neurim Pharmaceuticals (1991) Ltd & Anor v Generics UK Ltd (t\a MYLAN) [2020] EWHC 3270 (Pat) Mr Justice Marcus Smith made some observations about the role of the expert witness and the importance of their evidence being criticised in a written judgment.

“It is incumbent on the expert not merely to present evidence that is technically correct, but that makes a fair presentation of the expert’s opinion. If the expert does not do that, then criticism is liable to follow.”


The judge had sent the parties a draft written judgment in a dispute relating to a patent in relation to pharmaceutical formulations to improve the quality of sleep. Both sides called expert witnesses who produced reports and gave evidence at trial. The judgment contained criticisms of an expert witness called on behalf of the defendants.  After the draft was circulated counsel for the defendant suggested that the criticism of the expert was unfair as they had not had the chance to respond to it.


The judge considered the general issues relating to the expert evidence called by each party.

“I am, thus, very conscious that I was presented with experts in two distinct but overlapping fields, and I bear that in mind when consider the evidence of both Professors. But I find Professor Morgan to be as much an expert in his field as Professor Roth was in his own.
(f)           Professor Morgan gave his evidence calmly and with, on the face of it, a subdued authority. Unlike Professor Roth, whose specialism was sleep medicine, Professor Morgan considered the phenomenon of sleep in the aged rather more holistically, to include aspects not related to sleep medicine (such as cognitive behavioural therapy). Inevitably, this meant that his knowledge in relation to the pharmacological aspects of sleep was shallower than that of Professor Roth (who, conversely, had less knowledge than Professor Morgan in relation to these non-pharmacological aspects of sleep). I see this, quite simply, as a function of the different nature of the expertise of the two Professors. However, since the matters in issue between the parties concern sleep medicine, it is unsurprising (as I find) that Professor Roth spoke with greater weight that Professor Morgan on the key issues.
(g)          Unlike Professor Roth, Professor Morgan was far less conversant with patents and the concepts and issues underlying patent litigation. Again, I stress that this is in no way a criticism, but it did represent a real problem in terms of the weight to be attached to Professor Morgan’s evidence. As I describe, the skilled person not merely has a common general knowledge in the matter at hand, he or she also has something of a grasp of patents and their operation. Professor Morgan lacked this, and it became evident at times during the course of his evidence that he was reading the Patent in a way that the skilled person would not.
(h)          The last point that I make in relation to Professor Morgan’s evidence concerns less his oral evidence and more the written reports he submitted before the hearing and which he affirmed represented his expert opinion when he gave his evidence in-chief. I am afraid that Morgan 1 and Morgan 2 (Morgan 3 is a short and not particularly material report) were, in critical respects, disingenuous documents, written in a manner that seemed to me calculated, not to assist, but to mislead, the court. I am very conscious that this is the most serious criticism that one can make of an expert, and I do not make it lightly. The main points that have compelled me to this conclusion are dealt with fully in paragraphs 62 and 67 of this judgment, and I have sought to be clear throughout this judgment why I am not accepting evidence on certain points. Because the points go very much to the substance of the issue that I must determine, it is not possible to anticipate them here, save in the most general of terms. Suffice it to say, for the reasons given in these paragraphs, I am not confident that I can rely on Professor Morgan’s reports, save with a degree of caution and reserve that a judge would not normally attach to the report of an expert.
(i)            As is normal practice, a draft of this judgment was circulated, on terms of strict confidentiality, to the parties and their legal advisors. Professor Morgan did not see the draft. Counsel for Mylan – in addition to identifying typographical errors and making other points – questioned the appropriateness of my criticisms of Professor Morgan, and referred me to the decision of the Court of Appeal in Re W ([2016] EWCA Civ 1140), a case which considered (in rather different circumstances) the extent to which it was appropriate to make factual findings in relation to persons not directly before the court (i.e., witnesses not parties), but named as part of a fact-finding exercise conducted by a judge in the Family Court. Whilst I do not consider Re W to be precisely on point, I have re-visited the draft with Mylan’s points regarding Professor Morgan specifically in mind. I am grateful to Mylan for raising the matter so clearly – it was right to do so. However, having considered the matter most carefully, I have not materially changed the terms of the draft, and I should explain why:
(i)           An expert is responsible for his or her evidence, including the precise wording of any report submitted to the court under the name of that expert. In many cases, the expert will be in need of, and will receive, assistance from the solicitors (or other lawyers) who have retained that expert. That is entirely understandable, but only serves to enhance the importance of the expert being entirely satisfied that his or her opinion is properly reflected in the report(s) submitted in that expert’s name. This is the duty of the expert, and it is not one that can be delegated.
(ii)          An expert will be giving opinion evidence in relation to a subject-matter with which a lay person – specifically, in this case, the judge – will be unfamiliar. That is why the evidence is needed. It is incumbent on the expert not merely to present evidence that is technically correct, but that makes a fair presentation of the expert’s opinion. If the expert does not do that, then criticism is liable to follow.
(iii)         It must be emphasised that such criticism is not intended in any way to be personal or punitive. It is an intrinsic part of assessing the weight to be attached by the court to the expert evidence that is adduced before it. The criticisms that I have made of Professor Morgan must be seen in this light. They are made purely and simply because I need to explain to the reader of this judgment precisely why I have preferred – on critical points – the evidence of Professor Roth over that of Professor Morgan. That has involved a very close parsing of material parts of Professor Morgan’s written evidence, together with the oral evidence he gave in relation to that written evidence.
(iv)         To put the same point differently: it would be unacceptable for me to say simply that I preferred the evidence of Professor Roth over that of Professor Morgan, without saying why. Oftentimes, the “why” will turn on technical matters of legitimate dispute between the experts, and the judge will explain why the approach of one expert has been preferred over that of another, it being accepted that each expert was doing his or her best to assist the court. That is the ordinary case. This – for reasons that I have set out in this judgment – is not such a case.  
(v)          The suggestion was made that the substance of the criticisms I have made of Professor Morgan’s evidence were not put to Professor Morgan. I do not accept this contention. All of the aspects of Professor Morgan’s reports that I have seen fit to criticise were put to Professor Morgan by Mr Waugh, QC. I have – as is my duty – drawn my own conclusions from the totality of the evidence. The manner and form in which I have evaluated Professor Morgan’s evidence in light of the totality of the evidence is – as it should be – a matter for me.”