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Expert Evidence part 3

Experts in civil proceedings are supposed to be there to assist the court on matters falling within their expertise. They are not supposed to be there as hired guns. The expert is instructed by one side, he is paid by that side, but he has to remember that it is his duty to help the court on matters within his expertise and that that duty overrides any obligation to the person from whom he is paid or has received instructions (CPR 35.3).

Experts have a number of duties laid down in case law and now summarised in the protocol for the instruction of experts attached to part 35 CPR, and in particular 35.19. They have to be aware of the overriding objective (CPR 1.1) under which the court has to deal with cases justly. Experts have to assist the court to enable it to deal with matters in that way (although obviously it is for the court to make the decisions not the expert). An expert should not be an advocate, and should always be independent. A useful check for them to operate is suggested to be whether they would be giving the same opinion if the other side had instructed them. (One may wonder what is the point of having an expert if they are truly independent, but there is still an importance which is twofold: expert evidence may be necessary to supplement or explain a part of your case so that you can be confident that an expert can fairly and independently assist you but is necessary in order to fill those gaps; likewise if you instruct him not only can you make sure that he is investigating and answering the right questions in which you want to focus on, but if he is genuinely an independent expert then he should act in that way and his evidence is more likely to be accepted by the court than if he appears to be partisan. Experts who appear to be mouthpieces for their clients are not only failing in their duties, but they are likely to be regarded as useless by the court and hence have their opinions disregarded).

A crucial requirement is that experts provide opinions only in relation to matters lying within their expertise and that they should indicate where questions or issues fall outside their expertise. This is critical. Sometimes comment can stray across a number of disciplines. In some of them a person may be expert but not others. It is very easy to assume that they are expert in everything and that is why the expert must indicate where the limits of his expertise lie. Otherwise the court can end up acting on conjecture rather than expert comment, however genuine and well-intentioned that conjecture is.

In addition if an expert considers that more information is required in order to reach a proper opinion that must be stated. Similarly if an expert's view changes they should inform those instructing them without delay of the change and the reasons for it. (For example they might have seen a paper with new research which changes some of the fundamentals, whether that is referred to in the other side's experts report or otherwise comes to their attention).

Michael J. Booth QC