I recently attended an international arbitration conference in Europe, which included a session on expert witnesses. Comments from several participants displayed a surprising lack of understanding of the role, with several people saying that if lawyers and their clients engaged an independent expert and paid his or her fees, then that expert should support their case.

I discussed the matter with colleagues who are experienced international lawyers and arbitrators, and they told me that they regularly experience exactly this type of misunderstanding and (sometimes) blatant misuse of expert witnesses.

Therefore, this article seeks to provide an overview of the role, summarize the essential principles, and produce concise guidelines that one should follow in accepting and undertaking an appointment as an expert. These links and case references primarily reflect United Kingdom protocols and law, with some from the United States.

Expert witnesses and expert evidence defined

The Royal Institution of Chartered Surveyors (RICS) in the U.S. and the U.K. provides an apt definition for an expert witness:

“An expert witness is a person engaged to give an opinion based on experience, knowledge, and expertise. The overriding duty of an expert witness is to provide independent, impartial, and unbiased evidence to the court or tribunal.”

There is an important difference between opinion evidence from a layperson and an expert in regard to what is acceptable evidence. Lay witness evidence is normally restricted to factual matters that are within someone’s personal knowledge; he or she is not permitted to express opinions.

Evidence from an expert is used when the evaluation of the issues in dispute involves technical or other subject knowledge that only real experts would have and that would likely be outside the knowledge of laypersons and those trying the case.

Primary duties and responsibilities of an expert witness

Expert witnesses have a primary obligation to assist the court or tribunal on matters falling within their expertise and are not bound to the party that has appointed them and is paying their fees. This is quite often misunderstood, and it is common for clients and their legal advisers to lean on experts to make their opinion supportive of the client’s case. This compromises the independence of the expert and should be strongly resisted, to the point of turning down the appointment. The client is free to appoint an expert adviser for this purpose if they so desire (see below).

In Ikarian Reefer (U.K.), Mr. Justice Cresswell provided a succinct summary:

“A misunderstanding on the part of some of the expert witnesses has taken place concerning their duties and responsibilities, which has contributed to the length of the trial.”

He then proceeded to outline the duties and responsibilities of expert witnesses in civil cases. Among them were:

• Facts or assumptions upon which the opinion is based should be stated together with material facts, which could detract from the concluded opinion.

• An expert witness should make it clear when a question or issue falls outside his or her expertise.

• If the opinion was not properly researched because insufficient data was available, then that has to be stated with an indication that the opinion is provisional. If the witness cannot assert that the report contains the truth, the whole truth, and nothing but the truth, then that qualification should be stated on the report. 

• If, after exchange of reports, an expert witness changes his or her mind on a material matter, then the change of view should be communicated to the other side through legal representatives without delay and, when appropriate, to the court.

The findings in the report must be signed off as being those of the expert only, based on the facts provided and the expert’s own expertise. If the report was prepared with the assistance of a team, the lead expert must understand and agree with every detail in it, as he or she will be the only one in the witness box.

Resist any pressure to slant a report toward a party’s case; do not compromise your independence. You can clarify points, but do not alter your basic findings unless new evidence changes your assessment. Any partiality or bias will be detected and will be damaging to your professional reputation.

The difference between an expert adviser and an expert witness

This difference should be clear, at least to lawyers, but this is where misunderstanding remains. Independence is the key to this difference. An expert witness has a primary obligation to provide an independent, impartial, and objective assessment to the court or arbitration tribunal, which supersedes his or her duty to the instructing party.

This independent opinion may not turn out to support the case of the instructing party or counter the evidence of the other party, but professional experts will not be swayed by who appointed them in arriving at their conclusions. If the report does not suit the appointing party, then it may not be able to just bury it in the bottom drawer, because this is not allowed in some jurisdictions. Expert advisers have quite a different role. As well as providing their opinion and advice to clients, they can also discuss related matters and case strategies, knowing they will not have to appear as witnesses and be cross-examined, or have their opinions critically reviewed by other experts. Advice provided by an expert adviser is privileged. 

Qualifying as an expert

Experts are generally approached because of their reputation in a field, but prior to appointment, they will normally be asked to affirm that they have real expertise in the specific issues identified in the brief. Sometimes parties will invite someone to participate as an expert who may be wellknown in the industry but not a particular expert on the specific issues in question. In this situation, the appointment should be declined. It is far wiser to decline than to expose yourself to the risk of being humiliated by real experts and opposing counsel in a hearing.

Accepting expert appointments

Experts need to confirm that they have real expertise in the required area, providing detailed information that satisfies the appointing party. Experts should make a declaration that they have no conflict of interest, or alternatively provide a statement advising of a relationship with one of parties but confirming that they will be able to act impartially, as well as explaining why. Perceived conflict of interest can be a difficult area and probably should be avoided by declining the appointment, even for those who feel they can act impartially. The fees for experts are normally payable by the appointing party, or become a cost of the case if appointed by the court/tribunal, and they should not be contingent on the outcome of the case.

Disclosure of expert reports, instructions, and briefing documents

It is common for parties to think they can bury an expert’s report in the bottom drawer because it does not support their case, treating it as privileged. However, this is not necessarily the situation. If the opposing party hears that an undisclosed expert report exists, then it may be able to request an order that it be tabled and that the author appears as an expert witness. This will depend on the rules for the particular jurisdiction. There is no general rule across jurisdictions in regard to privilege and disclosure of instructions, case material supplied, draft reports, and undisclosed expert witness reports. A safe way to proceed is to assume that all communications between legal advisers and experts have the potential to be disclosed to the opposing party. 

Professional liability and immunity

Provided an expert maintains a high standard of care and professionalism in accordance with his or her jurisdictional rules, professional negligence should not be an issue. Nevertheless, a prudent practitioner should carry PI insurance, mainly to cover the costs of defense in the event of a challenge on some basis, such as a technical error that influences a proceeding and leads to an unjust finding against a party.

In Jones v. Kaney [2011], the U.K. Supreme Court decided that expert witnesses did not have immunity from claims for professional negligence. This reversed a line of authority dating back 400 years.