Hot-tubbing in UK Courtrooms

The concept of “hot-tubbing” has attracted a lot of attention amongst civil litigation academics and expert witness groups in recent years. Unfortunately, it does not involve a group of scantily clad lawyers sitting around in a hot tub, but the implications are [almost] as interesting. Hot-tubbing, formally called “concurrent evidence”, is an Australian import. The basic idea is that all expert witnesses in a particular area are examined simultaneously by the court under oath and after the lay evidence has been heard, although there are a number of variations. During the “hot tub” the experts are usually permitted to ask each other questions and to summarise their positions in the light of all the evidence given before normal cross examination takes place[i]. The practice was devised for use in the Australian Trade Practices Tribunal (now the Competition Tribunal) and adopted by the Federal Court. It was considered and recommended by the Jackson Review of Civil Litigation[ii] and is now the subject of a pilot scheme in Manchester[iii]. The theory has it that this practice cuts down the time required to hear expert evidence and so saves costs[iv]. But is it likely to be a valuable addition to the court’s tool box or merely a fashionable red herring?

Although the Australian version of hot-tubbing has been well described by Heerey elsewhere[v], it is not clear what model is being trialled in England and Wales. In any case, most forms are said to have a number of benefits for the conduct of civil litigation. First, the evidence will be as focussed as possible. This is so because, by the time the hot-tubbing begins, all of the lay evidence will have been given and so it will be clear where the key disputes lie, and which facts are effectively agreed. In addition, the experts usually have an opportunity to summarise their positions before and after the hot tub takes place. This makes it likely that the areas of disagreement between the experts themselves are clear and that they are addressed in the evidence. Further, in the model described by the Jackson report[vi], the experts have sat down together before the hearing and made a list of disagreements between them, which acts as an agenda at trial. As a result of all of this, there is (human nature aside) an absolute minimum of wasted time in the examination and the evidence is as useful as possible.

Second, two forms of bias may be reduced or eliminated by using the hot tub. Former Master of the Rolls Anthony Clarke, writing extra-judicially, called these “personal” and “structural” biases[vii]. Personal bias is that tendency of witnesses in the adversarial system to side, subconsciously or otherwise, with the party that instructs them. Its causes are described in a stinging attack on the adversarial system by Geoffrey Davies, a former senior judge in Queensland[viii] (see further below: text to n.15). Placing the expert amongst a group of his peers detaches him from his own “team” and reinforces the fact that he is primarily there in order to assist the court[ix]. “Structural bias”, on the other hand, denotes a bundle of underlying hypotheses, working assumptions and theoretical standpoints, which inform the position of an expert. Allowing his fellow experts to expose and question these is likely to give the judge a greater understanding of the basis for the opinion and a better idea of how valuable it is. It must be remembered that, at the end of the day, it is up to the judge to choose between competing opinions in fields which are by definition outside his area of expertise[x]. The elimination of bias has obvious beneficial results for civil justice.

Third, the worst excesses of the adversarial process are to some extent curbed by the process. It has been noted countless times that cross examination may seem unnecessarily aggressive to a lay person and that witnesses are often upset by the process. Less than skilful handling of an expert may lead to their adoption of a prickly or defensive attitude. This may reduce the quality of the evidence and draw out the process, as counsel must take some time over testing it. Further, it has been argued that “[t]raditional sequential cross-examination of experts may appear to many people to be artificial and susceptible of being manipulated unfairly, if perfectly honestly, by clever advocates”[xi]. In the hot tub process, by contrast, the majority of the questioning is likely to come from the expert’s peers and “[i]n effect a brief colloquium takes place[xii]”. The expert is likely to respond better to this sort of “scholarly” discussion and the nature of the discussion itself will dilute any accusations of manipulation directed at subsequent cross examination. And finally, Heerey makes the observation that the judge has the benefit of seeing all of the experts together, allowing him to contrast their performance as witnesses more effectively[xiii].

I have already referred to Geoffrey Davies’ trenchant criticism of the adversarial approach. It is worth outlining his views briefly as they have some force. Davies performs an interesting thought experiment in which he first invites us to imagine designing a system for resolving questions requiring expert knowledge from scratch. He then invites us to imagine that one proposal is that a lay person should decide the answer after hearing two different expert opinions on the subject and asks what our reaction might be. He concludes that we would “dismiss it as bizarre”[xiv]. Surely a panel of experts, people who understand the argument, should decide the question? As should be clear, the core of the argument is that adversarial argument is not a rational or efficient way to resolve “expert” questions.

Davies identifies three key problems. First (and most importantly) bias leads to polarisation of the opinions of the experts[xv]. The trial preparation, in which lawyers seek to have their experts present their clients’ “truth” in the best light, encourages extreme views. This means that both the question and the answer are presented as a polar choice when the real issues are far more nuanced. Second, Davies points out that a non-expert judge will have difficulty understanding the problem and finding a rational basis for his conclusions[xvi]. Third, the counsel in the case undertake cross examination of the experts. This has two consequences, the first being that, as non-experts, they too do not fully understand what is being discussed and so do not always ask the right questions[xvii]. The second is that counsel are there, not in order to assist the court, but to persuade the judge that their “truth” is the correct one. The result is that they do not promote an understanding of the problem before the court[xviii]. Davies adds that all of the effort devoted to preparation and examination in an adversarial system costs substantial time and money.

To Davies, the use of the hot tub is simply a method of eliminating the worst of the polarisation since it will inevitably occur too late in the process to do any more than produce a compromise, which will not necessarily reflect the right answer, but rather the best accommodation of the opposing positions of the parties[xix].The gist of his solution is the adoption of a system of court appointed experts who would be available on the initiative of the parties or of the court itself[xx]. A single[xxi] expert would be appointed, before commencing litigation if necessary, to resolve all questions in his field. The proposal would allow for case preparation and settlement in the knowledge of the expert view at trial, thereby eliminating polarisation. This has now become law in the state of Queensland[xxii] and will, according to Davies, eliminate adversarial bias. Despite Davies’ views, it is unlikely that such a system will be implemented in England and Wales soon but it is interesting to note in the context of Lord Neuberger’s recent remarks about moving away from the adversarial approach[xxiii].

Despite the purported advantages there is at least one major criticism that can be levelled at a system such as the one just described. It is predicated on the assumption that there is a discrete question of expert evidence, which can be resolved neatly. Most civil trials are not this straightforward; often the facts are completely disputed and an expert might be forced to make, in effect, two reports. This would entail duplication and a necessary polarisation, as he would have no choice but to assume each party’s version of the facts to be correct for the purposes of the two answers. Take the example of workplace safety: party A alleges a floor was littered with obstacles and covered in slippery fluid; party B claims the rubbish was stacked neatly to one side and the fluid was dealt with properly. The expert on health and safety would probably have to say: on version A there has been a breach of health and safety rules for reasons w and x. However, on version B there is no breach for reasons y and z. Compare this to the discrete issue of how to predict the price of coal discussed by Davies[xxiv].

Since we are not moving far away from the adversarial system it might seem that the introduction of hot-tubbing is a desirable reform in this jurisdiction. However, it must be remembered that we already have a numerous mechanisms for controlling the use of expert evidence, most of which apply before the parties have got anywhere near the courtroom. In this context, it is pertinent to ask whether the problem of costs is being taken seriously now and what effect the use of new techniques will have. For example, the CPR[xxv] already requires the parties to consider alternative dispute resolution (“ADR”) procedures. It is likely that in many cases where expert evidence is needed the use of “expert determination”, a process in which an independent expert issues a binding decision on the expert question, would be suitable. In other cases the inherent uncertainty of expert evidence should make mediation attractive. Once trial has begun the court has both the power under CPR part 35 and the duty under part 1 to control the use of evidence, the fees charged, and so on; it is even presumed that expert evidence is to be given in written form rather than under examination by counsel[xxvi]. Further, the experts themselves owe a duty to the court above the one they owe to their clients, and this should be rigorously enforced. Moreover, the court has the power to require the use of “single joint experts” on issues as well as to allow written questions to experts from the parties and discussions between experts alone (without parties or counsel). If all of this machinery is failing to sufficiently reduce the time and expense which expert evidence costs the civil litigation system then can it be said that a new piece of machinery will do so? If the evidence really has to be this lengthy and complex why have the parties not baulked at the cost and settled?

It will of course be argued that hot-tubbing is designed for use in those most complex cases which feature bitterly opposed experts and parties who refuse to settle for their own good reasons (perhaps to set a precedent). However, there is no reason why the expert question should not be settled as a separate issue before trial, leaving only legal questions to be argued. There is also the risk of abuse in cases where extensive expert evidence is not really necessary. While hot-tubbing is a system which appears to have saved time and costs in practice, and is therefore probably a “good thing”, it must not be allowed to legitimise the over indulgence in expert evidence or to distract the court from its duty to control the evidence before it in the interests of justice.

Tom Bradfield
King’s College London

[i]Heerey, Peter; Recent Australian Developments, (2004) (23) CJQ 386, 390

[ii] Jackson, Rupert; Review of Civil Litigation Costs: Final Report, (TSO 2010) 469, <> Accessed 5 December 2011

[iv]Ibid 390-1 & 395.Heerey describes a case in which the evidence of two experts on bank interchange payments and five economists took a day each.

[v] See n.3, above

[vi]Jackson (n.1) 593

[vii] Clarke, Anthony; The Role of the Expert After Woolf, (2008) (14) (No 3) Clinical Risk 85, 91

[viii] Davies, Geoffrey L.; Current issues – expert evidence: court appointed experts (2004) CJQ (23) 367, 368-370

[ix] Civil Procedure Rules 1998 (“CPR”) r.35.3, see also Jackson, Review of Civil Litigation Costs: Preliminary Report (Vol 2) (TSO 2009) 593

[x] Experts may only give opinion evidence on areas outside the normal expertise of the court: Buckley v Thomas (1554) Plowd 118

[xi]Neuberger, David; “EWI Annual Conference Keynote Address” (Expert Witness Institute Annual Conference 5th October 2011) para. 14

[xii]Heerey (n.3) 391

[xiii] Ibid

[xiv]Davies (n.8) 367

[xv] Ibid 368-370

[xvi] Ibid 371

[xvii] Ibid 368

[xviii] Ibid 371

[xix] Ibid 372

[xx] Ibid 373-374

[xxi] Some exceptions apply.

[xxii] Uniform Civil Procedure Amendment Rule (No. 1) No.115 2004 (Queensland, AUS),  <> Accessed 5 December 2011

[xxiii]Neuberger, (n.11) para. 15

[xxiv] Davies (n.8) 371. The issue in question was simply how a person should value a coal mine. This could easily be separated from the facts (i.e. the specific characteristics of the coal mine in issue).

[xxv] See, in particular, Pt.1 and PD Pre Action Conduct

[xxvi] CPR r.35.5

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