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Claim No: IL-2025-000064 - [2025] EWHC 2545 (Ch)
Fecha: 06-Oct-2025
Expert evidence: legal principles
Expert evidence: legal principles
On the admission of expert evidence, I was taken to CPR 35.1 and 35.4. I was also taken to the following authorities: Barings Plc v Coopers & Lybrand [2001] PNLR 379 at paragraph 45 per Evans-Lombe J; Clifford v Chief Constable of the Hertfordshire Constabulary [2008] EWHC 2549 (QB) at paragraphs 26 and 31 per Wynn Williams J; British Airways Plc v Spencer [2015] EWHC 2477 (Ch) at paragraph 63, 68 and 69 per Warren J; The RBS Rights Issue Litigation [2015] EWHC 3433 (Ch) at paragraph 18 per Hildyard J; Astex Therapeutics Ltd v AstraZeneca AB [2017] EWHC 1442 (Ch) at paragraph 42 per Arnold J; Bridgewater Associates LP v Minicone 16 July 2020 (Employment Arbitration Tribunal); AlphaSharp Ltd v ADG Capital Management LLP [2021] EWHC 1779 (Comm) at paragraph 38 per Waksman J: and Henderson & Jones Ltd v Salica Investments Ltd [2025] EWHC 475 (Comm) at paragraphs 235-6 per Calver J.
From these authorities, I derive the following propositions:
Expert evidence is admissible in any case where the court accepts that there exists a recognised expertise governed by recognised standards and rules of conduct capable of influencing the court’s decision on any of the issues which it has to decide; and the witness to be called satisfies the court that he has a sufficient familiarity with and knowledge of the expertise in question to render his opinion potentially of value in resolving any of those issues.
Evidence which meets this test can still be excluded if the court takes the view that calling it will not be helpful to the court in resolving any issue in the case justly. Such evidence will not be helpful where the issue to be decided is one of law, or is otherwise one on which the court is able to come to a fully informed decision without hearing such evidence.
Expert evidence cannot assist in resolving a pure issue of disputed fact. This falls to be determined on the factual evidence. This may be subject to a qualification that I tentatively identify in the following paragraph of this judgment.
- Heading
- Introduction
- Background
- Case management issues
- Disclosure: legal principles
- The first three of these propositions may be distilled from McParland , the fourth from Lombard North Central , and the fifth from PRS v Qatar Airways Group
- Multiple, and overlapping, issues for disclosure should be avoided wherever possible
- Disclosure: Submissions, analysis and conclusions
- I have not yet decided whether this should form one of the issues for disclosure. But if it were to do so, then it would seem to me to eliminate all need for disclosure issue 4 since it makes it unnec
- To the claimants’ knowledge, the defendant could not have replicated Humber elsewhere. Accordingly, the claimants’ case with respect to any Springboard relief (insofar as it is based on the possibilit
- The defendant cannot see that this possibility has been considered by the claimants. The defendant is therefore concerned about the nature of any searches the claimants will have undertaken concerning
- Further, I consider that the claimants place too much emphasis upon the defendant’s own repeated assertions, in contemporaneous documents, that he could (and would) ‘replicate’ Humber (as reproduced a
- Expert evidence: legal principles
- The burden of establishing that expert evidence is both (i) admissible and (ii) reasonably required (in the sense that it is not just ‘potentially useful’ ) is on the party which seeks permission to a
- Barings is authority for propositions (1) and (2); Clifford for proposition (3); The RBS Rights Issue Litigation for proposition (4); British Airways for propositions (5) to (9); and Astex for proposi
- At p. 11, the tribunal described the respondents’ experts’ evidence as “ independent, impressively detailed and completely credible ,” and further that
- Ms Goodman submits that this arbitral decision demonstrates the utility of an expert in this type of assessment as lawyers are obviously ill-equipped to know, and the court will be ill-equipped to adj
- In Henderson & Jones Ltd v Salica Investments Ltd [2025] EWHC 475 (Comm) , Calver J (at paragraph 236) is said to have ordered expert evidence to assist in determining “ (i) whether the allegedly conf
- The decision tells the court nothing about whether or not expert evidence should be ordered in a case governed by the Civil Procedure Rules. That case involved an arbitration. Mr Craig KC rightly says
- Practical utility of confidential information The defendant proposes to rely on the expert evidence of Mr Colin Knight, a qualified trader with over 20 years’ experience in trading strategies. Ms Goodman points out that algorithmic trading was ac
- The claimants have themselves relied on the expert report of Mr Winrow to analyse the coding data extracted from the defendant’s electronic devices, as evidenced by A & O Shearman’s letter of 5 Septem
- It is the claimants who bear the burden of proof in this case, which concerns the nature, and value, of technical descriptions of algorithmic trading strategies and actual code. They are required to p
- Stage in trading strategy development – identifying which stage in the trading strategy development process each piece of ‘confidential information’ (as defined in the particulars of claim) pertained
- The assertion that there are a certain number of stages in the development of a trading strategy at G-Research is the defendant’s own construct , in the sense that it is not said to be a framework ref
- Public domain assessment – assessing whether the ‘confidential information’ was, as a matter of fact, generic and/or widespread industry knowledge within the field of quantitative investment, such tha
- The claimants emphasise that the defendant well knows that the information in issue in this case is not generic and/or widespread industry knowledge. That is precisely why he admits to saying (in an u
- Valuation of confidential information – determining the value of the ‘confidential information’ to a competitor, including with reference to various dates The claimants’ case is that the defendant well knows that Humber is highly valuable: see the co
- Retention of value – Assessing whether, and to what extent, the ‘confidential information’ is likely to retain its value over time, including over a one-year period of garden leave Quite apart from the disproportionate nature of the exercise (not lea
- Practical utility of confidential information – Assessing whether, and to what extent, other businesses (including Citadel Securities) could utilise the ‘confidential information’ in their business ac
- If material at all, this is a question of fact; but, in any event it is extremely difficult to understand how an expert would be able to opine on this matter: it suggests that there would be some reco
- Stage in trading strategy development The claimants submit that the assertion that there are a " number of stages in the development of a trading strategy " is a mere construct. The defendant contends that there is a logical difference be
- Public domain assessment
- The defendant submits that, at most, he referred to Humber at the highest degree of generality, and that the summary to which the court was referred was of minimal value. The parties are, accordingly
- Valuation of confidential information At paragraph 3 of their particulars of claim, the claimants plead that the claim " concerns the defendant's misuse and copying of the claimants' extremely valuable and sensitive confidential informati
- Retention of value Even if the defendant had the requisite knowledge and ability to ‘replicate’ Humber, establishing when Humber is likely to lose its value (through the process of alpha decay) will be the primary consi
- Practical utility of confidential information Conclusions