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The role of the expert witness explained

The key difference between a lay witness and an expert witness is that the former can only attest to fact whereas the latter may give evidence based upon opinion gathered from knowledge and experience of a particular field or discipline. Such opinion invariably takes the form of a report on which the expert may be examined as a witness in Court.

The role of the expert is to help the Court understand detailed technical or scientific issues deemed to be outside of its experience. His primary duty is to the Court which requires that any evidence given in the form of a report or orally must be complete in all relevant matters. This duty may sometimes run counter to the interests of the expert’s client, for example when unhelpful issues are raised or uncovered during his investigations and analysis. In this situation, the expert’s duty to the Court is paramount and any professional problems with the client may have to be resolved through the expert resigning his appointment.
The expert must be independent and objective in his or her opinions and evidence, and will have to sign a declaration confirming he has abided by his duty to the Court, including a statement of truth. Such independence requires that the expert has no financial interest in the outcome of a case precluding an appointment on the basis of “no-win, no-fee”.

Before the Civil Procedure Rules come into force in 1999, the traditional role of an expert witness was to represent the interests of one side. However, since then, it has become far more usual for an expert witness to be appointed jointly by the parties to a case as a single joint expert (“SJE”) rather than acting in a partisan role. Where the Court directs that a SJE be appointed the parties have to agree on the choice, which can sometimes be problematic, although in the final analysis the Court will decide if a consensus cannot be reached. The SJE must treat each party with equal consideration and ensure that they are each aware of all communications on the case, written or oral. It is not uncommon, even when a SJE has been appointed, that one or both sides employ a “shadow” expert to advise on the SJE’s conclusions.

We routinely prepare expert witness reports for litigation purposes, including commercial disputes, family law proceedings and actions between shareholders under the Companies’ Act 2006.