Traditionally, the role of expert witnesses was to supplement the court‘s common knowledge with any helpful information. More recently, however, experts have taken on a more central and amplified role as investigators with private knowledge.“
In 1996, Lord Woolf echoed the disquiet of the time felt at the role of experts in civil litigation:
“A large litigation support industry, generating a multi-million pound fee income, has grown up among professions such as accountants, architects and others, and new professions have developed, such as accident reconstruction experts. This goes against all principles of proportionality and access to justice. In my view, its most damaging effect is that it has created an ethos of what is acceptable, which has in turn filtered down to smaller cases.”
Lord Woolf was referring to a culture that had developed in civil cases in which it was regarded as normal, indeed usually essential, in cases of any complexity for both parties to arm themselves with an expert witness or witnesses. This had two undesirable consequences. First, the complexity and therefore inevitably the duration of litigation was increased by the use of such evidence on both sides. More particularly, as will be seen below, experts had become conscious of the fact that they were being paid by a particular party for a particular purpose and felt either consciously or otherwise to provide “value for money” in return for the increasingly inflated fees which they were able to command.. Accordingly, this undermined the integrity and the independence of witnesses who had come to be accorded a special status to the extent that the justification for such status and privileged treatment had disappeared. It is therefore necessary first to examine the reasons for expert evidence being treated differently from other types of evidence, in particular that of the partisan lay party.
The emphasis in a court of law has always been upon the proof of fact. Mere expressions of opinion are regarded as having, at best, little probative value and, at worst, as being objectionable as without weight and potentially misleading. However, there have always been exceptions to such a general exclusionary rule. Uglow opines:
“…an opinion can acquire weight: firstly by a witness testifying to the facts upon which he or she bases that opinion; secondly from the very status of the witness.”
It is submitted that this proposition is potentially misleading in two respects: first, while the admission of bare facts is regarded as the desirable norm, an opinion will not necessarily be rendered more valid by virtue of those facts being within the personal knowledge of the witness than if it is an opinion based on facts gleaned from elsewhere; second, as will be seen from an examination of the notorious Meadows case discussed below, the elevated status of a witness can be positively misleading in the sense that juries may be tempted to regard certain proposed conclusions as more likely to be true as a result of the eminence of the witness from whom they issue. This notwithstanding, the common law has always been prepared to admit expert evidence. In the ancient case of Folkes v Chadd, Lord Mansfield accepted the opinion evidence of a scientist as to causation:
“I cannot believe that where the question is, whether a defect arises from a natural or an artificial cause, the opinions of men of science are not to be received. Handwriting is proved every day by opinion; and for false evidence on such questions a man can be indicted for perjury…”
In a codified system such as that which operates in the USA, the admissibility of expert opinion is expressly provided for:
“If scientific, technical, or other specialised knowledge will assist the trier of fact to understand the evidence or to determine a fact in issue, a witness qualified as an expert by knowledge, skill, experience, training or education, may testify in the form of an opinion or otherwise [emphasis supplied]”.
The evidence of an expert is therefore founded upon his training and experience. It is permissible for an appropriately qualified expert to express an opinion based upon that which is, for him, necessarily hearsay. Thus, for example, a doctor would be able to give evidence of a diagnosis on the basis of symptoms described to him by a patient even though he would be incapable of attesting to the veracity of those symptoms which, if in dispute, would have to be proved by the introduction of other direct evidence. To this extent, the assertion that the traditional role of the expert witness was to “supplement the court’s common knowledge with any helpful information” can be justified: it is to be supposed that the purpose in calling such an expert is to allow the court access to information which would not otherw