When to appoint an expert witness
Where it is clear that expert evidence will be required, the sooner you instruct an expert the better. Not only will this give the expert first hand knowledge of the matter but it will also save him or her from having to read large volumes of documents, usually collated many months or even years after the event (which, of course, is time consuming and will be reflected in the expert’s fees). In addition, the expert will be in a position to provide valuable “on the spot” advice.
Thus, the prompt appointment of a suitably qualified expert is likely to result in a considerable saving of costs and will enhance the chances of success.
Leaving the appointment of an expert until the last minute can have disastrous results. Judges and Arbitrators do not look favourably on parties who wish to introduce expert evidence late in the day. Aside from being penalised on costs, there is a real risk that the Court and/or Tribunal will not allow late expert evidence to be relied on or referred to by a party. This will often substantially affect the outcome of the case.
Duties of an expert under English law
Broadly speaking, the function of any expert is to assist the Court/Tribunal on technical or other specialist areas by providing their impartial opinion on such matters. It is not the function of an expert to give their opinion on issues of law or fact. These are matters for a Judge or Tribunal to decide.
The duty owed by an expert to the Court or Tribunal overrides any obligation towards the party from whom their instructions are received and by whom they are paid. The Court/Tribunal is entitled to expect and receive independent, unbiased and impartial evidence from an expert on a particular issue. Thus, experts must deal with the evidence as a whole as opposed to simply concentrating on particular aspects which support the instructing party’s case.
In the event that an expert fails to comply with his or her obligations to the Court or Tribunal there is a real risk that their evidence will not be relied on. As it is often the case that expert evidence will determine whether or not a case is won or lost, the consequences of an expert’s failure to comply with his or her obligations to the Court or Tribunal and/or any undue influence from the party instructing him or her as to the contents of any expert evidence, will be serious and often fatal.
Expert evidence normally takes the form of a written report. At the end of an expert report, there will be a statement that the expert understands his or her duty to the Court and has complied with that. The expert must also sign a statement of truth confirming that that the matters stated therein are true to the best of his or her knowledge or belief. As experts must also refer in their reports to the instructions they have received (either written or oral directly from a party and/or their solicitors), it is important to think very carefully about the precise wording of any instructions. These instructions will not be privileged from inspection even if they are provided to an expert by a solicitor.
Experts must not be requested to, and nor should they, amend their reports in a manner which is inconsistent with their true opinion although amendments for the sake of clarity and/or accuracy, are allowed.
The above points can be illustrated neatly by the decision of the English High Court in Carpenter v Pembrokeshire County Council, 1st October 2002 (Unreported). In this case, the Court was very critical of a civil engineering expert who was clearly influenced by his client, the Claimant, to alter his opinions and various reports.
Whilst the expert in this case accepted that it was his duty to assist the Court (and not the Claimant) in determining the matter before it and also accepted that it was his duty to reach a balanced and independent view without being led or influenced in any way by the Claimant, he nevertheless, failed to comply with his obligations.
For instance, the expert considered it appropriate to refer to the service of the Court proceedings upon the Claimant, and to set out part of the history relating to the discovery of documents in the litigation, both of which were clearly issues of law and beyond his role as an expert.
He also referred to “without prejudice” settlement offers that had been made during the course of the proceedings.
Furthermore, when the expert was asked whether or not he had ever prepared a report and incorporated into it documents, he said that he had not done so. However, it was clear from one of his reports before the Court in this case, that two documents had in fact been prepared by the Claimant and attached to the report.

The Court accordingly took the view that the Claimant’s expert had adopted a “wholly surprising stance” on issues which had nothing to do with his expertise and was clearly confusing his role as an expert with that of a lawyer.

In circumstances where the independence of the Claimant’s expert’s opinion was in doubt, the Court rejected his evidence in favour of the Defendant’s expert and the Claimant lost her case.

Appoint your expert as soon as possible.

Think carefully about the precise wording of your instructions (as these will be referred to in the expert's report).

Resist the temptation to interfere with the expert's obligations towards the Court/Tribunal, namely to provide it with independent, unbiased and impartial evidence on a particular issue.


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