Skip to content

Paper delivered to the Australian Institute of Judicial Administration Expert Evidence Seminar, Melbourne
11 November 2005

Articles on problems with expert evidence usually begin by reciting paragraphs from judgments decrying the extent to which adversarial bias is encountered. A passage from a judgment of Sir George Jessell MR using the phrase "paid agents (1)" is often referred to. Lord Woolf has now joined the list. In his Access to Civil Justice Report, he said this:

"Expert witnesses used to be genuinely independent experts. Men of outstanding eminence in their field. Today they are in practice hired guns. There is a new breed of litigation hangers-on, whose main expertise is to craft reports which will conceal anything that might be to the disadvantage of their clients. (2)"

His words are contemporary; but what he said is very little different to what Sir George Jessell had said more than 100 years earlier. It is readily concluded that conventional methods for receiving expert evidence are defective. Reform is called for. The kind of reform which is most popular relies upon single expert witnesses, often court appointed.

The procedure contended for limits evidence on any field of expert knowledge to one witness. The parties are either to agree on the witness or the witness is appointed by the Court. The witness remains a conventional witness. The witness is neither an assessor nor a referee.

Justice Davies, now retired from the Supreme Court of Queensland, has been a principle advocate of the need for change. More recently, he has been joined by Justice McClellan of the New South Wales Land and Environment Court and now of the Supreme Court of New South Wales. The New South Wales Law Reform Commission has recently reported on Expert Witnesses (3). Proposals for single expert witnesses are central to their recommendations.

The purpose of this paper is to present a contrary view: to suggest that the problem is not so serious and the solution required is not so drastic.

One of the members of the New South Wales Law Reform Commission who was involved with the Expert Evidence Report is the Hon. Hal Sperling QC, a retired judge of the Supreme Court of New South Wales. I recently heard him interviewed by Terry Lane on his Sunday ABC Radio programme "The National Interest" (4). His subject was the Expert Evidence Report. To the best of my recollection he said this:

"I will give you an illustration from my own experience. As a judge I heard a case in which the critical issue was whether a surgeon had left a radioactive substance in the lungs of a patient. If he had, the plaintiff won. If he had not, the plaintiff lost. Two experts gave evidence.

Their evidence was based on the same X-ray of the patients lungs. One said it was obvious that the substance was in the lungs. It clearly appeared from the X-ray. The other said the X-ray showed only common deviations within the norm. Now what is a judge to do with that?"

My immediate reaction was that what a judge should not "do with that" is to ask a single expert to decide.

Before my present appointments I spent more than 32 years practising at the bar. I saw many expert witnesses. They included one who won the Nobel Prize for Medicine for two separate discoveries (beta-blockers and anti-ulcer drugs) (5). There were also valuers, planners, accountants, scientists, doctors, engineers and many more. Many of the witnesses were not world class experts. Many of them made a substantial part of their living from writing expert reports and supporting them in court hearings.

I must say that my impression from 32 years of examining expert witnesses and four years of listening to them is that, with very few exceptions, they do not deliberately mould their evidence to suit the case of the party retaining them. When they do, it is obvious. They do expose the matters which support the hypothesis which most favours the party calling them. Provided the matters are legitimate and that any doubt as to the strength of the hypothesis is exposed, I see nothing wrong with this. Indeed, I think this process is one of the great values of the traditional approach to expert evidence. It is exposing different expert points of view for evaluation by the judge.

A small proportion of disputes end in litigation. A small proportion of those go to a hearing. Parties do not persist with losing cases. It is not my perception that they seek to convert losing cases into winning cases by subborning expert witnesses. The few cases of this which do emerge are the exceptions proving the rule. In the vast bulk of cases proceeding to hearing the reason is that there is genuine doubt as to where the merits lie. In cases involving areas of expert knowledge that is where some of the doubts are found.

It seems to be accepted that the best way to determine who said what in a contract negotiation, or what side of the road a motor car was on, is by hearing evidence presented by both sides. The function of a judge is to hear both sides and make findings of fact. Sometimes this is very difficult because memories of conversations are not good or even because the extreme self interest of parties may cause them to tailor an answer. This seems to be accepted as an essential part of the system. There is no alternative. The judge just has to decide where the truth lies. I wonder why expert evidence is thought to be any different; why those who accept the burden of resolving some evidentiary disputes find accepting the same burden objectionable when the subject matter of the evidence is a field of expert knowledge. To the extent to which requiring expert evidence to be given by one witness determines any issue it seems to me that there is a surrender of part of the judicial function. The role of judges is to make difficult decisions in circumstances in which no objective verification of the decision is available. Countless judges must have made wrong findings as to oral terms of contracts because they believed the wrong witnesses. The system should keep those situations to a minimum; but they exist. The role of a judge includes assessing where the truth lies in situations of conflict. I do not see why this role is any different or any less well achieved where the subject of the conflict is a field of expert knowledge.

If adversarial bias has been a prominent topic for debate over many years, so has the role of expert evidence. There is no easy line to be drawn between what is properly a subject for expert evidence and what is not. Two propositions seem clear. First, expert evidence only has a role to play when it has been established that there is a relevant field of expert knowledge. Secondly, the role of the expert is not simply to arrive at a conclusion but to expose criteria which will enable that conclusion to be evaluated (6).

The ultimate decision-maker must always be the judge. Expert opinion plays a subservient role. The first question is whether the issue is a matter for expert opinion at all. If it is, the final decision lies with the judge even if there is only one expert witness. However, in cases where there is an issue on a field of expertise and there is only one expert witness the requirement to expose criteria to enable a conclusion to be evaluated seems somewhat pointless when there is no alternative opinion available.

Let me return to Mr Sperling's illustration. Of course, the evidence before him was not confined to the experts' assertion and counter assertion as he described them. The evidence would not have been admissible if it was. Is not the most satisfactory way to resolve the difference, for a judge, part of whose expertise should lie in being able to detect where the truth lies, to resolve the dispute by reference to its context and the criteria identified by the experts? The problem with one expert in a situation such as that Mr Sperling described is that the expert might be either of the experts who actually gave evidence. That person may honestly strive to identify the competing expert view but will undoubtedly settle on the expert's own opinion. The result is that the case will be determined by the identity of the expert selected.

The fallacy underlying the one expert argument lies in the unstated premiss that in fields of expert knowledge there is only one answer. Of course, this is nonsense. The law is a field of expert knowledge. How often do the seven wise persons in Canberra arrive at the same answer, and for the same reasons? One wonders why appellate courts sit in banc, if one expert is enough, or why appellate courts are even necessary, if one person can be trusted to arrive at the correct result. The answer that is given is to say that single witnesses will not be appropriate in every case. My thesis is that they are rarely appropriate.

What might be a case in which a single expert is appropriate? Suppose the question is what is the background noise level at the site of a proposed development. That is a matter for measurement with the aid of an instrument. There is usually only one answer. That might well be a matter for a single expert. However, what if, unknown to the operator, the instrument is wrongly calibrated or defective? Moreover, the selection of the time and place to make the measurement is subjective. Most importantly, the significant evidence generally given by such witnesses is a prediction of the noise level after the development has occurred. That is just the sort of matter in which a better result will flow from a diversity of expert opinion. Finally, if the instruments are in good order and properly employed there will generally be no dispute at the hearing as to what the background noise level is. No expert evidence is required.

Some of the proponents of single experts consider they fulfil an important role by avoiding time taken on issues which will not play a part in the ultimate resolution of the dispute (7). It seems to me that in such a case there should be no expert evidence at all. Case management should achieve this if the parties do not see it for themselves.

When disputes survive until hearing there are generally matters bona fide and justifiably in dispute. Where can the differences lie when the dispute relates to fields of expert knowledge? First, there may be controversies within a discipline: is social isolation a risk factor in heart disease? Secondly, there may be different schools of thought: Freudian and non Freudian psychiatry. Thirdly, there may be different streams within one discipline: animal behaviourists whose careers have been in zoos may have different opinions to those whose careers have been in the wild. Fourthly, there may be different assumed facts: different histories for a person claiming employers compensation. Fifthly, even when the relevant body of expert knowledge is not in dispute one expert may come to a different conclusion from another when that body of knowledge is applied to known criteria: Mr Sperling's example.

In all these situations it is for the judge to decide and the judge will generally be better able to do that when working with honest expert assistance which nevertheless attempts to present the case from genuinely available differing perspectives. I do not find anything untoward in expert witnesses presenting different perspectives. This is what counsel do all the time. The limitation is that they must be sustainable perspectives presented in a way which can be evaluated. I do not even mind experts who are "hired guns" provided that they are not presenting evidence that is unsustainable, particularly where this could only be known by the expert.

I am conscious that there are emerging reports, both in England and Australia, that single expert evidence is working well. That is not surprising. The evidence will certainly be given efficiently. The task of the judge will be easier. The problem is that there is no way of testing whether the conclusions are correct. By definition there is nothing to test the expert evidence against. That seems to me to involve the rejection of one of the fundamental benefits of our system of justice.

It follows from the above that I do not share the concerns of some of my colleagues as to the extent of problems with expert evidence or with a single witness regime as at least one answer. There are, however, some problems with traditional methods of adducing expert evidence. Are there other responses which may enhance the quality of expert evidence?

The Administrative Appeals Tribunal has used what it calls concurrent evidence for many years. Its first significant use was in the hearing of Coonawarra Penola Wine Industry Association Inc and Geographical Indications Committee [2001] AATA 844. That case related to the use of the name Coonawarra by wine producers. An estimated six months hearing was reduced to five weeks.

I recently used concurrent evidence in a hearing concerning proposals by Melbourne and Sydney Zoos to import eight Asian elephants. There were sixteen expert witnesses and three senior counsel to examine them. The evidence of all sixteen witnesses was concluded within four hearing days. This was achieved notwithstanding that, although the experts all had doctorates in disciplines associated with animal behaviour, one group had worked in zoos and the other group had worked in the wild. As one senior counsel said:

"…it's very clear to all concerned that there is a great degree of polarisation of views on this subject." (8)

Nevertheless, the process enabled areas of agreement to be readily discovered and set to one side and issues of disagreement then to be effectively addressed. This happened although there were up to four witnesses giving evidence at the same time including one occasion when one of a group of four gave evidence by telephone from New Delhi. We also took concurrent evidence from two witnesses in the United Kingdom by video link although the two witnesses were in different parts of the United Kingdom.

All the witnesses had prepared extensive reports which became evidence. The process we adopted was to ask the witnesses to meet together to identify areas of agreement and disagreement. They were asked to produce a document setting this down. At the beginning of their evidence the document was admitted as an exhibit. Each witness was then asked to outline the essence of their evidence on matters not agreed. The witnesses were then invited to ask questions of one another. During the whole process members of the Tribunal asked questions when they thought it appropriate. Finally, counsel for the three parties were invited to question any of the witnesses including those they had called to give evidence.

The process of asking the experts to find areas of agreement and disagreement was very successful. The two who gave evidence from England both had doctorates. One was head of wildlife for the RSPCA. The other was the Director of the British and Irish Association of Zoos and Aquariums. They definitely gave evidence from different perspectives. They could only meet by telephone. They were a long way from the lawyers and any guidance as to how they should go about their meeting. Yet they produced a comprehensive multi-page document of points of agreement and disagreement.

The RSPCA officer, Dr Atkinson, began his oral statement like this:

"Okay. Thank you. There was a lot of agreement. Miranda and I met yesterday. We are both very welfare conscious people and we're anxious to improve the situation for captive elephants and we've both committed time and money to improvement. We are both aware of the limitations and the usefulness of the Mason Report and of the Wise and Willis Report on elephant mortality. We disagree on the benefits of freezing, breeding and the importation of elephants and we also disagree on the urge to breed earlier than would be the case in the wild." (9)

The Zoo Association Director, Dr Stevenson, followed, saying that she agreed with the way the areas of agreement and disagreement had just been outlined.

Concurrent evidence can have a number of virtues over the traditional process. First, the evidence on one topic is all given at the same time. Secondly, the process refines the issues to those that are essential. Thirdly, because the experts are confronting one another, they are much less likely to act adversarially. Fourthly, a narrowing and refining of areas of agreement and disagreement is achieved before cross examination. Fifthly, cross examination takes place in the presence of all the experts so that they can immediately be asked to comment on answers of colleagues.

I cannot see how a single expert, who must come from one range of experiences and possibly one school of thought, could have fairly put alternatives to the Tribunal and assisted it with its choice free from the expert's natural bias.

One answer which will be given is that these cases of expert evidence are atypical. The experts do not make any substantial part of their income from preparing expert reports and giving evidence. The answer to that is that the Administrative Appeals Tribunal does not confine its use of concurrent expert evidence to such cases. Indeed, the primary use of expert evidence in the Tribunal is in personal injury and illness cases such as Commonwealth Employees Compensation cases and Veterans' Entitlements cases. These are cases in which the expert evidence is largely the evidence of medical practitioners. They are the cases where, it is said, the same doctors always turn up on the same side.

The use of concurrent evidence in these cases has been the subject of an Administrative Appeals Tribunal study. The process was used in nearly 50 selected cases. Statistical information was recorded. Opinions were collected from tribunal members, legal representatives and the experts themselves. The effectiveness of the process was then evaluated in accordance with accepted scientific standards. I am pleased to be able to release the final report today. Copies of the Report are available to you all. I will not seek to go into the details of its findings. To recite the statistical results which appear in the paper would not be a good idea. However, they show that concurrent evidence is generally effective and broadly liked, even by lawyers.

In one of his judgements, Sir Owen Dixon relied upon the adage "one story is true until another is told (10)". I think we would do well to bear that in mind when dealing with expert evidence as we do when dealing with other evidence. Concurrent evidence recognises that the adage is as true of expert knowledge as of anything else; the use of single experts does not.

My purpose today has not been to advocate a norm for expert evidence. It has been to advise caution with respect to single or court appointed experts while recognising that there will be some occasions when they are useful. Much expert evidence will continue to be given in the conventional way. However, concurrent evidence can be an effective way of addressing areas of expert knowledge in nearly all cases. I commend it to courts and tribunals for consideration.


  1. Abringer v Ashton (1873) 17 LR Eq 358 at 374.

  2. Lord Woolf MR, Access to Justice, Interim Report to the Lord Chancellor on the Civil Justice System in England and Wales, HMSO, London, 1995, p. 183.

  3. Expert Witnesses (Report 109) June 2005.

  4. 16 October 2005.

  5. Sir James W Black: 1988 Nobel Prize in Physiology or Medicine.

  6. Per Haydon JA in Makita Pty Ltd v Sprowles (2001) 52 NSWLR 705 at 729(59) and 731(62).

  7. Justice Peter McClellan, Prosperity - cost effective justice? (a paper delivered to the Annual Conference of the Australian Institute of Judicial Administration on 18 September 2004) at pp. 5 & 13.

  8. International Fund for Elephant Welfare (Australia) Pty Ltd v Minister for Environment and Heritage Transcript 11 October 2005, p. 40.

  9. International Fund for Elephant Welfare (Australia) Pty Ltd v Minister for Environment and Heritage Transcript 18 October 2005, p. 456.

  10. Pontifical Society for the Propagation of the Faith v Scales (1962) 107 CLR 9 at 20.