Expert evidence in construction cases– a view from the tub

by Bart Kavanagh


At a recent event on negotiation skills at the Academy of Experts the speaker, a negotiator in international and domestic hostage situations, emphasised that the most important skill he needed was listening. And his first rule of listening? – don’t ask questions. His view, based on experience, was that people will say much more if they are not guarded and they are less likely to be guarded if they are allowed, or encouraged, to talk freely.

It’s a simple thought – if you want to hear something, you need to listen; if you need to listen, you need to let people talk. But let’s put this thought to one side for a few moments.

Our adversarial system

In the UK and other Common Law systems and in international arbitration, we are all familiar with the adversarial legal system that we, each in our own way, live and work with every day. Nevertheless, it is worth reviewing briefly the framework within which expert evidence sits.

The business of a trial, or other determinative hearing, is to take a set of factual events, consider the duties and obligations that are imposed under the applicable law, and apply it to the events. Questions of law are addressed in legal arguments, which are put forward by counsel and the opposing sides are permitted to test and challenge these arguments with respect to logic, relevance and other factors. Of course, our courts and tribunals come ready equipped with a joint independent expert on the law, variously addressed as ‘Sir/Ma’am’, ‘Your Honour’ or ‘My Lord/Lady’ depending on exactly which tribunal you find yourself in. This expert has the jurisdiction and competence to decide which legal argument, or counter argument is correct, or is to be preferred, and why.

Evidence of the facts or events that are at issue is presented and then tested and challenged regarding its veracity so that the relative strength of the opposing evidence can be determined by the tribunal. In our adversarial system the main tool for challenging and testing the veracity of evidence is cross examination. But here we need to stop and consider the differences between factual evidence and expert opinion evidence.

Factual evidence is provided by witnesses who can tell the court something that they saw or something that they know; a fact or series of facts. Witnesses of fact could mistake or misinterpret events or, on occasions, have been held simply to be mendacious. Cross examination can be an effective tool for demonstrating whether a witness is more, or less, reliable and credible than another witness.

Expert evidence is the expression of opinions, not facts and it is given by an expert with an express duty to the court, which overrides any duty to the client. There may be several related factual matters such as; is the expert suitably qualified with sufficient relevant experience in the matters at issue to be of assistance to the tribunal, which can only be tested in cross examination, but I would argue that cross examination alone will provide the tribunal with only limited assistance in fully understanding the technical aspects of expert evidence.

This is where we need to look again at the idea of listening that we considered at the beginning.

Cross examination is not an exercise in listening. Its purpose is to elicit only the specific information that counsel seeks in order to promote their client’s case or damage that of their opponent. It is designed to expose errors, deficiencies and inconsistencies in evidence in order to persuade the tribunal that an alternative proposition is more likely to be true.

Opinions, however, are not right or wrong and, in my view, they are not susceptible to testing by cross examination in the same way as matters of fact. Whether an opinion is honestly and genuinely held by an expert, and is based on reasoned analysis and argument, or is designed simply to bolster his client’s case, is more likely to be apparent in open discussion with a peer than in cross examination. There are several reasons for this. Counsel is likely to: have limited understanding of the technicalities under consideration; want the expert’s views to be presented to the tribunal in a manner that best suits the purposes of his own arguments; and want to avoid questioning the expert on matters that may undermine his own argument. These factors are likely to restrict, or colour, the evidence that is presented.

Hot tubbing

Hot tubbing can provide the tribunal with the opportunity of listening to open discussions of technical matters directly. It may also elicit or elucidate subtle differences in the analysis and reasoning of the experts that are unlikely to be brought out in cross examination. This is likely to assist the tribunal’s proper understanding of the technical issues and help avoid the need simply to ‘prefer’ the evidence of one expert over another or, more accurately, prefer the way in which one expert responds to cross examination than the other.

If cross examination tends to be destructive, or manipulative, of the evidence presented, hot tubbing, on the other hand, should tend to provide the tribunal with a full and neutral understanding of the technical matters at issue.

I suggest also that there is a parallel between listening to open discussion of differing views on technical issues between two experts in the hot tub and the weighing up of the differing legal arguments that the independent legal expert, the tribunal, must go through in reaching a decision on the law.

This is not to suggest that the experts should in any way take on responsibility for answering ‘the ultimate question’. That task must still fall to the tribunal which must apply the law not only to the factual evidence but also to the opinion evidence in order to do so. I would strongly suggest, however, that the fullest understanding of all the evidence should provide the firmest basis for a rational judgment.