Steamy windows: Setting the correct temperature for hot tubbing in international arbitrations

07 Jan 2013

What could be more appropriate as temperatures in the UK plunge to their lowest for 20 years than a look at the pros and cons of hot tubbing?

Much has been written about this subject but for the uninitiated this taking of oral evidence (usually from experts) “hot tub” style, means having expert witnesses being questioned and cross-examined together – firstly by the judge or arbitrators and then by the parties’ representatives themselves – and indeed even by each other!  Known in polite circles as concurrent evidence, hot tubbing can be used to great effect in construction related disputes, such as those involving design and build issues, measurement disputes, delays, and financial loss.

The TCC Guide recognises hot tubbing as one of the options for the Court to consider in deciding how best to deal with the expert evidence. Clause 13.8.2(d) sets out the option as follows:

“For the experts for all parties to be called to give concurrent evidence, colloquially referred to as "hot-tubbing". When this method is adopted there is generally a need for experts to be cross-examined on general matters and key issues before they are invited to give evidence concurrently on particular issues.

Procedures vary but, for instance, a party may ask its expert to explain his or her view on an issue, then ask the other party's expert for his or her view on that issue and then return to that party's expert for a comment on that view.

Alternatively, or in addition, questions may be asked by the judge or the experts themselves may each ask the other questions.

The process is often most useful where there are a large number of items to be dealt with and the procedure allows the court to have the evidence on each item dealt with on the same occasion rather than having the evidence divided with the inability to have each expert's views expressed clearly. Frequently, it allows the extent of agreement and reason for disagreement to be seen more clearly.

The giving of concurrent evidence may be consented to by the parties and the judge will consider whether, in the absence of consent, any particular method of concurrent evidence is appropriate in the light of the provisions of the CPR.”

It all sounds spectacularly straightforward and quicker.  But is it in fact better?  Well whether or not it is any better, or indeed any worse is arguably academic, as the process is both here to stay and is gathering momentum.  The discussion therefore now needs to move on towards examining the best ways of managing the process, so as to ensure that your experts are able to perform as effectively as possible. For first time hot tubbers the process can appear to be wholly alien and so it is useful to be aware of a few basic ground rules in advance, as you never know when that hot tub moment will come about. 

Getting into the hot tub mindset

In the minds of the hot tub purists, gone now are the days of the dogged attempts by counsel to discredit experts by trashing their CV’s and trying to force them to accept the age old proposition that, “in fact this is the first time you have ever been an expert isn’t it?”.

Whilst the reality of hot tubbing is not perhaps as extreme, the dispute resolution story has firmly moved on and the world is moving towards the hot tub approach, particularly in the slightly more relaxed setting of international arbitrations, where the process is becoming increasingly popular – not least because of the very real time pressures on both the parties and more importantly upon the Tribunal to ensure that hearings complete within the allocated time.  With parties often having travelled long distances to attend hearings, it is simply not practical (or indeed possible) to extend hearings. 

Furthermore, the witnesses of fact often take far longer than parties expect and so by the time it is time for the experts to give their evidence, the hot tub represents the best (and indeed sometimes only) option for ensuring that the hearing is completed on time.

Of course this is not to say that time pressures aside that the hot tub is not also a good option per se but what is essential is for everyone involved, especially the experts themselves, is to know well in advance what is going to happen – tribunals have been known to announce during the actual arbitral hearing that they are going to hear the experts together.  Indeed it is not uncommon for a time pressed but urbane Chairman to “announce” with great charm that the tribunal would like to do is to hear the experts together and then come up with an all too hastily thought out plan as to how in fact this is going to actually work.  This is not in anyone’s interests and so it is essential for all parties to know from the outset of the proceedings whether a particular tribunal is minded to adopt the hot tub method or not.

Therefore the first point is to know, perhaps even before the experts are selected, whether a particular tribunal is minded to adopt the hot tub approach; different experts might be more suitable to different methods of giving their evidence. If the answer is that that is a matter for the parties, then make sure it is a matter which is decided upon between the parties at the earliest possible stage.  Even the thickest skinned expert might baulk if suddenly told that he or she is required to make a 30 minute presentation in front of a decision making panel at a few hours’ notice – this level of excitement is the preserve of counsel!

The view from the tub

So assuming a "tub situation", the norm in international arbitration is for each expert – prior to being asked any questions is to be given up to 30-40 minutes to make an uninterrupted oral presentation to the tribunal, which can – and often does – include power point presentations.  If one expert has colourful slides to show the tribunal and the other simply reads from a text, then human nature being what it is, the focus of attention of the tribunal will be drawn inevitably to the slides.  Of course by this stage the experts have been invited to try and narrow the issues as much as possible, so as to reduce the scope of their evidence –either by the preparation of a joint report or an agreed list of issues which remain incapable of agreement. However they will rarely reach full agreement and so there is always likely to be a “competition for votes” if you like and so the more persuasive the initial presentation the better.

In the TCC, as indicated by the TCC Guide, it appears to be envisaged that there might be cross examination first and then an element of hot tubbing. This is certainly how Ramsay J made use of it in Harrison v Shepherd Homes [2011] EWHC 1811 (TCC).

There is of course no hard and fast rule about how the hot tub process should work and this has led many practitioners to suggest that there should be published guidance or protocol in respect of the hot tub process.  This quasi “statutory underpinning” to borrow the in vogue press related expression is not necessary and what is just as effective is for the parties themselves to agree upon a procedure in advance.  The key is that everyone should be clear as to how the process will work and prepare accordingly.  Arbitral tribunals are more often than not willing to go along with what the parties have agreed in respect of procedures.  The whole point of the hot tub process is that it is both flexible and adaptable and so there is really no need for parties to be hidebound by protocol and nor is there any reason for parties not to be able to work out how the process will work in practice. 

Looking at the tub – “what the Tribunal saw…”

There may be occasions when tribunals indicate that they do not wish any oral submission from the experts at the start and will simply proceed straight to asking questions.  This is an approach which parties should be guarded against because the tribunal may not in fact have understood key elements and a short oral presentation uninterrupted by lawyers and arbitrators can be of significant assistance to all.  Therefore it is essential that when picking an expert parties satisfy themselves that they have someone who could – if so required – sell a vision to an arbitral tribunal and therefore also ensure that their expert will be able to make a presentation before any questions are asked.  It is one thing for a court or tribunal to express the view that they understand everything and therefore wish to dispense with oral submissions and another thing for the parties to be of the view that they have had every opportunity to advance and present their respective cases. 

The next thing for the parties to decide is how the hot tub will be configured and how for example the experts will be positioned in the hearing venue; will they be beside each other and is there enough room for manoeuvre and for files?
The biggest fear is experts going completely off message and undoing a lot of good.  This is usually the result of being unprepared and/or unclear as to both the purpose of hot tubbing and also on occasion of the other side’s case. 

The whole question of concurrent evidence is also relevant at the very start of the process when regard is had to the suitability of an arbitrator.  Whilst in many large arbitrations the tribunal Chairman will be picked by an arbitral body, there are circumstances where there is only to be one arbitrator and so it is important for parties to ask themselves whether a potential arbitrator would – where applicable – be able to control a concurrent evidence session involving expert witnesses?  An expert is often the most knowledgeable person in the room in respect of his or her subject and if allowed to take control of the hot tub could gain an unfair advantage by appearing to be the more knowledgeable – largely upon the basis of having spoken more and giving the appearance of being in control. 

“What the Tribunal did next…”

So how does the questioning of the expert in the tub work in practice?  Will the tribunal effectively cross examine the experts or will they give them topics to discuss between them?   It very much depends upon how much (in reality) the tribunal understands about the subject matter, the experts’ reports and the list of issues which remain by the time of the tubbing.  If they are unclear they will invite the experts to comment on relatively general propositions which can give well prepared experts the upper hand.  At the end of the day each tribunal will adopt a different approach and there are no hard and fast rules. 

There is no doubt that an impressive sounding witness can make a fellow expert appear to be less of an expert and this is something which has to be watched.  In the same way that a party would select counsel with the ability to present clearly and if required forcefully, the same test if you like is needed in respect of expert witnesses too.  Experts now need to be able not only to stand up to cross examination but they need to be able “to keep their end up” in the face of attacks (however disguised) by a fellow expert.  One cannot underestimate the rivalry that exists between experts – particularly in narrow fields.

“But what about us?”

So after this so called collegiate discussion between the experts and the tribunal, with the parties’ lawyers having to grin and bear it how long will there be for each party to cross examine the other side’s witness?

Whilst the creation of a collegiate atmosphere may very well create a much more relaxed atmosphere, such an atmosphere will be of assistance to the more wily and experienced expert witnesses who excel when not under pressure.  Therefore it is vitally important to ensure that there is adequate time in the process to enable counsel to cross examine their opponents’ experts and, if so required, put them under the same sort of pressures that they would have been the norm under the old system. 

There is a tendency in arbitrations for this period to be seen as a slight afterthought by tribunals.  It should not be and the legal representatives must insist upon appropriate amount of time for cross examination after the tribunal have asked their questions and the experts have “questioned” each other.  As long as this fundamental right is protected then there is little to fear.  Without it, the giving of concurrent evidence is a gift to a more persuasive oral expert. 

Remember history is littered with great persuaders – often without regard to, or being necessarily troubled about the accuracy of their sentiments – who were masters at selling imperfect pictures of reality.  Without cross examination, concurrent evidence could be as dangerous. 

The road ahead

In summary, is the quality of the evidence of the experts improved by the hot tub approach?  Probably not and the real beneficiary of the hot tub is time but these days of course the premium of time is an important one.

The Manchester TCC hot-tubbing pilot, which ran from 2010 to 2011, reported back earlier this year (based on a very small number of cases). Their preliminary observations were that the process was generally well received and was thought to save time and enhance focus on the real issues in dispute, although there were concerns that the process was less rigorous than the more traditional approach.

However, hot tubbing is clearly here to stay and so the trick is to make sure that you are prepared for it right from the start.  As long as you are well prepared and make sure that there is adequate provision for cross examination, all in all it can in fact provide a much more relaxed environment for suggesting to seemingly highly qualified people that they really don’t know what they are talking about.  Just like the old days…


This content is provided free of charge for information purposes only. It does not constitute legal advice and should not be relied on as such. No responsibility for the accuracy and/or correctness of the information and commentary set out in the article, or for any consequences of relying on it, is assumed or accepted by any member of Chambers or by Chambers as a whole.


Please note that we do not give legal advice on individual cases which may relate to this content other than by way of formal instruction of a member of Gatehouse Chambers. However, if you have any other queries about this content please contact: