Hot-tubbing

Specialist Mercantile Judge, HHJ Waksman QC, explains how hot-tubbing, by saving time and narrowing differences, has a role in reducing costs under the new regime

What is hot-tubbing?
Hot-tubbing is the colloquial name given to the process of taking expert evidence concurrently at trial. So instead of the expert evidence being taken sequentially, the experts go into the witness box together. This allows the judge and/or the advocates to question them on a specific point at the same time – and usually the response from one will be followed immediately with a response from the other. Sometimes they will make follow-up comments or even question each other but all under the direction of the judge. The actual procedure to be adopted in any given case may vary and is a matter for the judge’s discretion. The process has been likened to a structured dialogue facilitated by the judge.


Following a successful pilot scheme in Manchester, an amendment to PD35, included in the raft of procedural reforms to come into effect on 1 April 2013, states as follows:

“11.1 At any stage in the proceedings the court may direct that some or all of the experts from like disciplines shall give their evidence concurrently.  The following procedure shall then apply.

11.2 The court may direct that the parties agree an agenda for the taking of concurrent evidence, based upon the areas of disagreement identified in the experts’ joint statements made pursuant to rule 35.12.

11.3 At the appropriate time the relevant experts will each take the oath or affirm. Unless the court orders otherwise, the experts will then address the items on the agenda in the manner set out in paragraph 11.4.

11.4 In relation to each issue on the agenda, and subject to the judge’s discretion to modify the procedure:

a. The judge may initiate the discussion by asking the experts, in turn, for their views. Once an expert has expressed a view the judge may ask questions about it. At one or more appropriate stages when questioning a particular expert, the judge may invite the other expert to comment or to ask his own questions of the first expert.

b. After the process set out in (a) has been completed for all the experts, the parties’ representatives may ask questions of them. While such questioning may be designed to test the correctness of an expert’s view, or seek clarification of it, it should not cover ground which has been fully explored already. In general a full cross-examination or re-examination is neither necessary nor appropriate.

c. After the process set out in (b) has been completed, the judge may summarise the experts’ different positions on the issue and ask them to confirm or correct that summary.”

But as noted above, the process may differ in a particular case. Sometimes, for example, there may be some cross-examination first. See paragraph 13.8.2 of the TCC Guide (Second Edition, October 2010).

The Court can order hot-tubbing at any stage. Often it may be done at the first case management conference but it can be left to the pre-trial review or even the trial itself if events so dictate. Experience has shown that the earlier the possibility of hot-tubbing is canvassed, the better, because it gives the parties and their experts a chance to consider it without the pressure of an impending trial.

Why have concurrent expert evidence at all?
There are two principal potential advantages both of which lead to a saving of time and costs. First in the course of the structured dialogue the experts may well narrow their differences. Experience gained during the Manchester pilot confirmed this. Second, the process enables the Court to gain a more immediate and crisp understanding of the real differences between the experts on any given issue. This enables the judge to form a view more quickly

What sort of cases are appropriate for hot-tubbing?
It is unwise to attempt to define rigidly the classes of case where a concurrent expert evidence direction is appropriate. But there are some paradigm instances. For example, where the issue is one of valuation or some other spectrum of values it is particularly apposite because the prospect of narrowing the disagreement is clear. Another case might be where the expert issue is of a standard nature, for example in relation to the adequacy of a structural survey; or questions of materiality in the underwriting context; or in respect of a schedule of defects in a construction case. But even in a case where the expert issue is more arcane, a direction may be useful precisely because it enables the judge to further her understanding of the issue directly with the experts – even if they do not then narrow it. We know from those practising in the family jurisdiction that a form of hot-tubbing has been used to great effect in some care cases or where there have been injuries requiring findings of fact. And similarly in clinical negligence litigation.

Equally I have found it to be of particular use where the expert evidence was still being formulated and noted because of late issues arising at the trial itself. Such issues were addressed most effectively by the experts working through them together, facilitated by the judge*.

One area where a direction may be inappropriate is where there is a strong attack on the competence or integrity of the expert, where nothing less than a traditional cross-examination at the outset may suffice. Even here, however, the judge could decide to revert to concurrent evidence a little further down the line. But Counsel’s preference for “his” expert to sit beside him while cross-examining the other expert will not be a reason for not making a direction. Nor will the argument that if a direction is made the parties will “lose control” of their expert. There is in truth no control to lose. The expert must be independent and owes that duty to the Court. It may be that he will be more forthcoming or willing to concede points in the hot tub than when (as he might see it) he is subject to a hostile cross-examination designed to trip him up, but that is a point in favour of hot-tubbing not against it. Many experts to whom I have spoken have expressed just this view.

The parties may be particularly keen on hot-tubbing where the experts, though differing in their views, clearly respect each other and have a constructive modus vivendi. They may be even more keen if assured by the judge (as they should be) that he will be fully on top of the expert material before the trial.

Where does this leave the role of Counsel?
The expectation (reflected in PD35) is that the amount of cross-examination required should be reduced significantly in most if not all cases where hot-tubbing is used. But this is far from making the trial advocate redundant. First, he is likely to be much more involved than previously in ensuring that the experts’ joint meeting and the subsequent joint statement really do produce a clear and full list of the areas of disagreement which will form the agenda for the questions at trial. Second, both advocates will be required to assist the judge in fine-tuning and ordering the agenda items. Third, there are always likely to be some remaining questions from the advocates (in cross-examination and re-examination) especially where the ground between the experts has not narrowed, or not by very much. In those cases where the evidence has been given concurrently, the clear impression given by counsel was that they found the process helpful and constructive, and did not feel “done out of their job”.

What does the future hold?
I would predict that now that the court’s power to make a hot-tubbing order has been expressly enshrined in PD35, and with favourable reports of its early use, the process will be employed in an increasing number of cases. The scepticism or fears expressed by some practitioners when the pilot was first mooted have proved to be unfounded, and those who saw mock trials showing both the traditional and the hot-tubbing way of doing things were on the whole impressed by this initiative. Indeed it has been suggested to me that a possible next step is to direct a hot tubbing-session with the experts even before the main trial begins, because it may well provoke an earlier settlement.

All of that said, hot-tubbing is not put forward as a panacea for all expert issues, nor is it intended to be the default mode of taking expert evidence. But it is an option which should at least be considered in most cases**.

* For my observations about hot-tubbing in two particular cases, see Lancs. Fire v Fame Commercials [2010] EWHC 3297 (QB) para.3 and Hanext v Pathmeads [2012] EWHC 2485 (TCC) paras.22 and 29.

** For a detailed and absorbing account of the history and theory of hot-tubbing and an analysis of some recent cases, see the forthcoming article by Professor Hazel Genn in Civil Justice Quarterly.

HHJ Waksman QC Specialist Mercantile Judge, Northern Circuit

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