Using expert witnesses to resolve complex issues and provide independent perspective


Financier Worldwide Magazine

December 2018 Issue

For disputes involving the determination of highly complex, technical or specialised issues, it is common for the parties or the court arbitral tribunal to require evidence from expert witnesses. As an example, the use of expert witness evidence in construction and engineering disputes is commonplace, considering these types of disputes frequently involve the determination of claims of technical defects, delays and the quantification of various sums claimed, such as for unliquidated damages or completion costs.

Expert witnesses assist courts and arbitral tribunals to comprehend and understand complex and technical issues, where the judge or tribunal members may themselves not have the necessary knowledge or experience to undertake a proper consideration of the evidence and the issues.

Given the impact that expert evidence can have on the outcome of a dispute, parties should give due consideration to a variety of matters that go into the processes of appointing and working with expert witnesses. Below, we examine some important considerations that parties should consider in relation to party-appointed expert witnesses.

Purpose of expert witnesses

The role of an expert witness is markedly different from the role of a fact witness. Expert witnesses have specialised education, training and experience in their respective field. Unlike fact witnesses, expert witnesses also provide opinion evidence to courts and arbitral tribunals in respect of matters within their field of expertise.

Given an expert witness’ role, it is perhaps unsurprising that expert witnesses are required to act in an independent and impartial manner, to assist the court or tribunal on matters within their expertise. This duty to the court or arbitral tribunal is an overriding duty, despite the fact that an expert witness will have been appointed and paid by one of the parties to a dispute. For example, Rule 35.3 of the UK Civil Procedure Rules outlines the expert’s duty to the court in similar terms.

The requirement for an expert witness to maintain their independence and impartiality is of the utmost importance. It follows that an expert witness does not form part of a party’s legal team, nor should they act as an advocate for a party. Therefore, there are limitations and boundaries to working with expert witnesses that must be maintained in order not to compromise an expert witness’ independence.

However, in some circumstances it can be advantageous for a party to retain an ‘expert consultant’ in a dispute, in addition to an expert witness. An expert consultant differs from an expert witness in that, while the expert consultant is similarly an expert in their respective field, the expert consultant will not present evidence in a dispute and therefore owes no duty of independence or impartiality to a court or arbitral tribunal.

In early 2018, the London Court of International Arbitration (LCIA) published a note on ‘Experts in International Arbitration’ which stated that expert consultants may be engaged to explore and develop claims (or defences to claims) and can play an “invaluable role” in ensuring the technical details of such claims and defences are accurately represented.

While there are certainly benefits to engaging an expert consultant, parties should be mindful that the costs of expert consultants can be high, and should balance those costs against the benefits to be had from the expertise of an expert consultant.

Appointment of expert witnesses

Having a clear understanding of the issues in a dispute that require expert evidence is a fundamental step that should occur prior to the appointment of any expert witness. It is essential that an expert witness has the necessary education, training and experience to truly qualify them as an expert in the specific field relevant to the issues in dispute. It is of course desirable for a party’s appointed expert witness to have more relevant or specialised expertise than that of the opposing party’s expert witness.

The requirement for an expert witness to be independent and impartial is also an important consideration prior to appointment. Common practice dictates that a party should request an expert under consideration undertake all necessary conflict checks to ensure that there is no conflict of interest in the expert accepting an appointment, such as a current or prior relationship with one of the parties to the dispute.

The requirement for an expert witness to be independent is of paramount importance, and indeed the 2010 International Bar Association (IBA) rules – ‘Taking of Evidence in International Arbitration’ – require any party-appointed expert witness to provide in their expert report, a statement of “his or her independence from the Parties” and a statement regarding “his or her present and past relationship (if any) with any of the Parties, their legal advisors and the Arbitral Tribunal”.

As indicated by the IBA rules, a party may appoint an expert witness who has a present or past relationship with a party to a dispute, however caution should be taken if considering such an appointment as it can be a difficult task to overcome a perceived lack of impartiality and independence.

An increasingly common occurrence is for parties to also consider appointing expert witnesses from professional consultancy firms. In many cases these experts no longer practice in their respective professions in a full-time capacity and instead dedicate a large majority of their time to acting as expert witnesses in disputes. One of the key advantages in appointing experts of this nature is that they will be familiar with the roles and responsibilities of acting as an expert witness, and will have experience defending their opinions under cross-examination. However, where an expert witness lacks recent ‘hands-on’ experience, consideration should be given to the specific issues in dispute and whether this could be unfavourably received by a court or arbitral tribunal.

Expert reports and expert conferral

The primary source of expert evidence in a dispute generally takes the form of a report written by the expert witness, setting out their opinion on the issues in dispute. It is imperative that expert reports are structured clearly and logically to allow a court or arbitral tribunal to understand their opinions with ease. The use of technical jargon will not, for example, assist a court or tribunal to understand an expert’s opinion, unless it is clearly explained or defined in the expert’s report.

Expert witnesses are also sometimes assisted by others (generally from within the expert’s organisation) in the preparation of their report. While this practice is acceptable, experts who do not carefully review the work of others and ensure it can be adopted as their own opinion, risk being caught in a position where they are unable to explain or defend parts of their own expert report.

In addition to expert reports, a court or arbitral tribunal may require parties’ expert witnesses to meet and confer, with a view to the experts reaching agreement and narrowing the issues in dispute. Importantly, this conferral takes place on a ‘without prejudice’ basis, allowing the experts to be open and forthright in their discussions with each other. The experts will record matters of agreement (and sometimes matters of disagreement) in a formal joint statement, which forms part of the evidentiary record.

The process of expert conferral produces varying results, depending in part on how flexible and willing experts are to engage in the process. Where one party’s expert is particularly assertive or dominant, this can also be a cause for concern and expert witnesses should be encouraged to be wary of any overtly pressuring behaviour. In addition, expert conferral may not be overly useful where experts take a fundamentally different approach or methodology to considering the issues in dispute.

Oral testimony from expert witnesses

During trial, parties will almost certainly have the opportunity to cross-examine other parties’ expert witnesses. Cross-examination can be a stressful process for expert witnesses, particularly those with no or limited experience with cross-examination. Parties should ensure that their expert witnesses understand the nature and process of cross-examination so that they are not caught unaware on the stand. For example, expert witnesses should be aware that opposing counsel may seek to challenge an expert’s independence, credentials, experience and opinions.

In summary, expert witnesses play an important role in the resolution of many complicated and technical disputes. Parties should be mindful of their approach to appointing and working with expert witnesses and the various considerations that arise.


James Bremen is a partner and Brittney Nash is an associate at Quinn Emanuel Urquhart & Sullivan LLP. Mr Bremen can be contacted on +44 (0)20 7653 2270 or by email: Ms Nash can be contacted on +974 6695 3071 or by email:

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