The 4 Fundamentals

26 January 2022

Expert witnesses often play a critical role in the determination of disputes. Recent judgments have reiterated the importance of an expert witness’ independence and quality of expertise. This can be effectively achieved if the expert witness and their supporting team abide by four governing ‘fundamentals’:

  • Independence;
  • Expertise;
  • Accuracy; and
  • Clarity


Governed by Part 35 of the Civil Procedural Rules,[1] a testifying expert witness in England and Wales has an overriding duty to the court as opposed to the instructing legal team. Although appointed and remunerated by either the claimant or defendant, the expert must provide independent opinions irrespective of whether it is helpful to the case advocated by the appointing legal team.

In the recent High Court judgment of ECU v HSBC [2021], the Judge commented that ECU’s foreign exchange expert appeared to “wish to support the Claimant’s case by his evidence”.[2] The Judge expressed “considerable misgivings about the reliability of the opinions that he expresses in his reports and a concern that he has approached his analysis in a way which tended to confirm his views rather than put before the court a balanced view of the possible (and likely) conclusions which can properly be drawn from the available data”.[3] The outcome of this was that the Judge preferred and relied on the evidence of HSBC’s expert witness in making their judgment.

As it is routine and necessary for experts to work closely with the instructing legal team, it is incredibly easy for an expert witness to feel they are part of this legal team, advocating for the client and aiming to ‘win’ the case. This is not the expert’s role. Great care must be taken to ensure that the expert retains their independence and that advocacy (as required and expected of the legal team) does not influence or creep into the independent expert’s report. In the TCC judgment for Beattie Passive Norse Ltd & Anor v Canham Consulting Ltd [2021], the Judge highlighted multiple issues with Beattie’s structural engineering expert witness, including “exaggerated” criticisms of the defendant, and “constantly sought to advance the claimants’ case at the expense of expert objectivity”.[4] The decision in this case therefore applied “considerably lesser weight” to the opinions of the Beattie’s structural engineering expert.[5]

It is more helpful for the instructing lawyers and the client to have an expert witness provide a balanced and unbiased opinion to the court. An expert witness who is seen to be biased and to lack independence reflects poorly on the instructing side and is unhelpful to the court. This was demonstrated in the High Court judgment of McKillen v Tynan [2020], when the claimant’s expert witnesses were deemed to be insufficiently independent, meaning that their evidence had “no weight given their patent desire to advance a case made by Mr McKillen”.[6]


The right experience and expertise allows an expert to provide helpful, relevant commentary to the court. As an example, financial disputes often require specific, niche expertise and there may only be two or three suitable candidates who can provide the required expertise, with the relevant vintage (and with no conflict of interest).

A very real risk for an appointed expert witness is that they find themselves in a position where they are opining beyond their scope of expertise. This can occur where the instructing brief is vague or where experts are new to expert witness work and do not have the required independent support. This risk needs to be carefully managed, as illustrated by the Court of Appeal’s comments regarding the Serious Fraud Office’s Libor-rigging expert witness in R v Pabon [2018]: “Where Rowe went wrong – gravely wrong, as we have concluded – was to go further and enter into debate on topics, beyond or at the very outer edge of his expertise, principally STIR trading”.[7]


Accuracy and attention to detail are vital. Expert witnesses are required to provide their opinions to help the court understand and determine key issues. If the expert’s opinions are not based on fact, and logically determined, then the entire report and testimony will be called into question.

Expert witnesses must be clear and explicit in how they have reached their conclusions, explaining any assumptions made or limitations to their analysis. The High Court judgment of ECU v HSBC [2021] was complementary of HSBC’s foreign exchange expert commenting that he “had a detailed and comprehensive grasp of the matters in his report and that the opinions he expressed were clearly his own and were the product of careful analysis and consideration by him and not by others”.[8] In addition, the Judge commented that the Martello expert “was very fair and measured in giving evidence – he accepted when he was able to agree and did not try to argue a case for one side or the other”.[9]


It is pivotal that the expert’s views are communicated in a clear, jargon-free and robust manner. If the court struggles to understand or follow the expert’s thinking and conclusions, then there is every possibility that key elements of the expert’s analysis will not be accepted. Expert evidence is only one piece of a much wider picture and it is important that the expert evidence is communicated in such a way that it is useful to the court.

The Martello Difference

An industry expert can be an incredibly helpful tool for the court to understand and opine on niche or technical aspects of a case. However, for this to be effective, Martello considers it imperative that the expert witness abides by the four ‘fundamentals’. As an Irish judge helpfully explained “it is only because of their expertise and assumed independence that [experts] are entitled to offer opinion evidence on matters central to the court’s determination”.[10]

Martello is well-equipped to match the right expert armed with the right expertise to the right case. The financial services sector is a complex idiosyncratic industry with a multitude of highly specialised niche products. It can be challenging for people even within the industry to be expert in every product set, let alone those with little knowledge of financial services. This complexity has only increased in recent years with added layers of regulation.

Martello’s approach ensures we keep our four ‘fundamentals’ – independence, expertise, accuracy, and clarity – top of mind as we work with our team of expert witnesses and assist the legal teams instructing them. Martello provides experts with the right, independent guidance and support not only to craft their expert report, but to navigate the entire expert witness process (which goes beyond just one report), conduct data analysis and research, and to prepare for oral evidence in court.


[2] ECU v HSBC [2021] CL-2019-000068, paragraph 115.

[3] ECU v HSBC [2021] CL-2019-000068, paragraph 151.

[4] Beattie Passive Norse Ltd & Anor v Canham Consulting Ltd [2021] EWHC 1116 (TCC), paragraph 79.

[5] Beattie Passive Norse Ltd & Anor v Canham Consulting Ltd [2021] EWHC 1116 (TCC), paragraph 86.

[6] McKillen v Tynan [2020] IEHC 189, paragraph 99.

[7] R v Pabon [2018] EWCA Crim 420, paragraph 69.

[8] ECU v HSBC [2021] CL-2019-000068, paragraph 153.

[9] ECU v HSBC [2021] CL-2019-000068, paragraph 177.

[10] Emerald Meats Limited v The Minister for Agriculture, Ireland & The Attorney General [2012] IESC 48, paragraph 28.