Expert evidence — overviewInstructing an expert

When instructing an expert, it is helpful to produce checklists of, for example, sources which may identify potential experts, issues to consider and questions to be addressed. These will help to give a focused approach. It is also important to appreciate that there are a variety of factors which need to be considered when instructing an expert other than their expertise. For example, whether there are conflicts of interest and the extent of the expert's communication skills, particularly if they have not previously given evidence in hearings.

A written letter of instruction should set out all of the information required by the expert to produce his/her report. An example of issues to be addressed are the timing of the proceedings. It is also essential to set out the experts duties and role as expert.

The permission of the court is required to appoint an expert and is generally sought at the Case Management Conference. However, experts can be appointed prior to commencement of proceedings and some pre-action protocols require this.

Expert report

An expert's report must be independent, uninfluenced by the processes of litigation, objective and unbiased.

The CPR sets out the requirements for an expert report; in particular, the expert must state that he/she understands and will comply with his/her duty to the court. They must also provide a statement of truth. A conflict of interest statement has also been recommended by the Court of Appeal.

Expert reports are exchanged, generally simultaneously and the other party seek clarification of your expert's report in the form of written questions. The experts will generally be required by the court to prepare a statement of issues on which they agree and disagree.

Parties may change experts. Depending on the stage of the proceedings, permission of the court maybe required.

An expert does not have blanket immunity but proceedings cannot be brought against them in respect of any evidence that they give. Proceedings could be brought, for example, if an expert breached regulatory codes.

Experts and assessors

Experts maybe witnesses (duty to the court) or advisers (duty to the client). There are a number of differences between the two:

• Expert witness owe a duty to the court and therefore must be independent of the party that appointed them. Communications between the expert witness and the party that appointed them are not generally confidential

• Expert advisers do not owe a duty to the court and therefore are not independent of the party that appointed them. All communications with the adviser in relation to the dispute and the proceedings are confidential

As a consequence of the differences between expert witnesses and advisers, advisers can be a valuable addition to a legal team, particularly on complex technical issues. An adviser may later become a witness but there maybe a question mark as to their independence.

Assessors are appointed by the court due to their expertise so that they may assist the court with complex technical issues or those unfamiliar to the court. Parties can object to the appointment. The costs of an assessor are met by the parties.

Single joint experts

The courts can order that expert evidence be provided by a single joint expert (SJE). This is the preferred approach in small claims and fast track cases. If the parties cannot agree on the SJE, the court can make the appointment or direct a selection process. An SJE should receive agreed joint instructions from the parties, if this is not possible, parties must provide each other with copies of their own instructions to the expert. All other communications must also be made available to the other side. A party can seek clarification of a report by written questions to the expert and may ultimately challenge the report's conclusions.