Expert evidence: the roles and responsibilities of the expert witness

Jonathan Hadley Piggin examines exactly what makes an ‘expert’ an ‘expert witness’ and why, when it comes to the court process – an individual needs to be much more than simply knowledgeable in order to be deemed an expert witness.

By definition, an expert is someone who – by reason of his/her education, training, skill or experience – has specialist knowledge of a particular field or discipline beyond that of a layman, such that other people may rely on his opinion about issues within his area of expertise.

What is expert evidence?

Essentially, expert evidence is opinion evidence or, the opinion of the expert. The primary function of the expert witness is to assist the court in reaching its decision by providing independent expert/technical analysis and opinion on an issue(s), based on the information provided by those instructing him. The expert evidence should provide as much detail as is necessary to convince the judge that the expert’s opinions are well founded.

Admissibility of expert evidence

Generally expert evidence is admissible whenever there are matters at issue which require the input of an expert for their observation, analysis or description. However, the Court has the power to exclude expert evidence in certain circumstances, for example when it deals with matters that are for the judge to decide or if on the facts of the case the judge can form his/her own conclusion without the help of an expert. The court also has the power, to reject evidence that is otherwise admissible, for example, if it decides that an expert has not established his independence or has not complied with his overriding duty to the court.

In large or complex cases the court may allow each party to instruct their own expert and if expert evidence is required in more than one area of expertise the court will usually allow the appointment of more than one expert, provided that the cost is proportionate to the value of the dispute. In less complex cases the court has the power to order that the parties instruct a single joint expert who is appointed and instructed jointly by the parties involved in the dispute.

Duties of an expert witness

The primary duty of an expert witness is to the court; this overrides any obligation to the instructing and paying party or parties. Expert evidence should be independent, objective and unbiased. In particular, an expert witness must not be biased towards the party responsible for paying his fee. In providing a written report and oral evidence the expert should be truthful as to fact, thorough in technical reasoning, provide his honest opinion and ensure that the report is complete in its coverage of relevant matters.

The duties an expert witness owes to the court may sometimes conflict with those he owes to the client. The most obvious example is when the expert’s conclusions contradict the client’s case. If the client seeks to put pressure on the expert to alter his report or suppress the damaging opinion the expert witness must resist such pressure, and if necessary should terminate his appointment.

Nor should an expert witness ignore information that may come to light which is damaging to his client’s case. There is always the risk that the other side will also be aware of it. In any event, the expert’s duty to the court requires that his evidence is complete in its coverage of relevant matters.

The expert witness should bear in mind that as well as his overriding duty to the court, at the same time, when accepting instructions, he also assumes a responsibility to his client to carry out his investigations with due care and to provide opinion evidence that is soundly based. The expert should therefore only undertake instructions that he is competent/qualified to carry out and only provide opinions that are within his area of expertise. If a matter is outside his expertise he should state this.

Finally, expert witnesses should ensure that they are familiar with the provisions of Part 35 of the Civil Procedure Rules and the related Practice Direction as this sets out the requirements that the expert must comply with when preparing his report, including the form of the report.

Instructions and privilege

The expert witness is required to set out all material instructions in his expert report(s). These instructions are not protected by privilege. Where a party has instructed an expert prior to issuing proceedings, if that expert is then appointed as an expert for the purposes of the court proceedings, the instructions provided prior to the commencement of the proceedings will usually be protected by privilege from disclosure to the other party. However, to ensure that such instructions are not disclosable, new instructions should be provided to the expert, as court-appointed expert.

Discussions between experts and evidence at trial

The court will usually order that the experts are to meet before the Trial date in order to discuss the issues in dispute and which they have not agreed upon. In smaller cases these meeting may take place by telephone rather than a face to face meeting. Following this meeting the experts should produce a joint statement setting out the matters on which they agree and the areas of disagreement, including the reasons for such disagreeme

An expert can only give evidence at the Trial with the permission of the court. Usually such permission is given.

Experts should note that they do not have immunity from a claim for negligence or breach of duty arising out of their preparation and presentation of evidence for the purpose of court proceedings, but an opposing party cannot bring a claim against an expert.