Menu Search through site content What are you looking for?

All in it together - new guidelines on witness hot-tubbing

  • Legal Development 3 October 2019 3 October 2019
  • Commercial Disputes

The process of allowing experts or other witnesses to give their evidence together can be difficult to manage. We explore valuable new guidelines that should help counsel - and arbitrators - with this challenging task.

All in it together - new guidelines on witness hot-tubbing

Earlier this year, the Chartered Institute of Arbitrators' (CIArb) Singapore branch published new guidelines and model directions on witness conferencing.  This is a very welcome development, given the lack of materials on this subject up to now.

The guidelines take the form of a checklist with copious notes, and directions that are both general and specific.  The general directions are intended for use mainly at the outset of proceedings, when it is not known how much evidence should be given in this form, or indeed whether witness conferencing should be used at all.  The more detailed directions are for use when the suitability of the procedure has been established and the tribunal needs to decide the extent of any witness conferencing, and how it should be managed.  The directions are also annotated fully, although here the guidance is likely of more use to newcomers, perhaps, than to experienced practitioners.

This technique of taking evidence from more than one witness in a 'conference', i.e. at roughly the same time, is not new or particularly revolutionary.   From one point of view it is just the culmination of a long-term trend.  Traditionally, parties presented sequentially (in English courts, at least), with the claimant arguing its case and putting forward all its documentary and oral evidence first, and the defendant doing the same after the claimant had finished.  In a small or technically simple case, that might work well enough, but where the hearing takes weeks or even months to complete and/or the issues addressed in the evidence are more technical, it is obviously not helpful for the judge or tribunal to hear expert witnesses, in particular, several weeks apart. The traditional approach has therefore evolved gradually into a more flexible one, where parties' evidence is interleaved, and it is quite common now, even in the courts, for experts to be cross-examined in turn, issue by issue, so that a judge can compare directly what they have to say.

Multiple forms and names

When a tribunal orders witness conferencing, the precise way in which the tribunal deals with the experts depends partly on the arbitrators' preferences, but also on the nature of the evidence and how it relates to the dispute. The simplest approach is for the tribunal to take the lead and cross-examine experts from like disciplines together, with the experts also quizzing each other when appropriate and counsel asking a few mop-up questions at the end.  However, other approaches are possible too, for example experts leading the session and asking the initial questions.  Helpfully, CIArb caters for each of the main options with alternative, tailored directions.

The fact that the procedure takes different forms is part of the reason why it goes by several names: witness conferencing, concurrent witness evidence, and hot-tubbing.  The latter term appears to originate in Australia, where the technique is used in the courts.  Other countries whose courts have adopted it to a greater or lesser extent include the UK and Singapore. 

In the English courts, witness conferencing was promoted by Sir Rupert Jackson as part of his costs reforms six years ago, although the procedure has not been used as widely as he hoped, despite the English Civil Procedure Rules providing for it in suitable cases (paragraph 11 of Practice Direction 35).

In Singapore there are no rules or guidelines that encourage or discourage witness conferencing in the courts generally.  It is discretionary.  However, in the Singapore International Commercial Court (SICC) the court is given a nudge in this direction.  Paragraph 90 of the SICC Practice Directions states that "the Court may direct that the evidence of several experts be taken concurrently", and there is an added health warning that, where this procedure is adopted: "in general, a full cross-examination or re-examination is neither necessary nor appropriate".  However, the Practice Directions make clear that the manner in which concurrent expert evidence is to be taken is always at the discretion of the court.

The term 'hot-tubbing' suggests a degree of informality but also, perhaps, that the expert is in some sense exposed.  Not all witnesses cope well with the procedure; a hired gun can be easily rumbled, for example. If she is a seasoned professional expert, she may cope well with cross examination, but in discussion with another expert her bias may be clear.  Experts can founder for other reasons too.  The dynamic between two witnesses can be unhelpful, for instance, particularly where one is more senior and the other relatively junior.  Then the young expert may not want to challenge the older one, and the latter may resent his authority being questioned.  This is a particular problem in certain cultural contexts, and can be acute where the junior expert has studied under the more senior one (as has been the case in some well-known examples where witness conferencing has not worked well).  Unfortunately this situation is sometimes impossible to avoid when the area of expertise is narrow and one's opponent has taken steps to conflict all obvious candidates for the expert role. This problem, and others like it, are explored fully in the new guidelines.


For the most part the guidelines are helpful without being particularly controversial  -  a compendium of good advice and model wording for all circumstances.  However, they do contain a few surprises.

To start with, one would expect the drafting team to have banged the drum for witness-conferencing, promoting it as modern and cost-effective, and therefore a generally desirable way of taking expert evidence in arbitration.  However, the opposite impression is often given.  This is partly the result, no doubt, of CIArb taking into account practitioners' views, canvassed during a consultation that preceded publication of the guidelines.  Many lawyers (the authors included) are ambivalent about the procedure.   They may have seen it work well, but they have also seen it come off the rails, for example where the experts have different degrees of fluency in the language of the arbitration so that the procedure either doesn't work or is obviously unfair, or where an expert cannot cope with the procedure and undermines his client's case at the eleventh hour.  It can also add to the costs of a case, since it is an additional procedure, not a substitute for the preparatory steps that have to be taken anyway.

The next surprise is the abundance of detail in the guidelines.  This is impressive, but occasionally overwhelming. 

Finally, there is an optimistic sense that when problems are identified, they can generally be dealt with adequately if they are anticipated far enough in advance and suitable preparations are made.  However, it is worth bearing in mind that in some cases it is simply a bad idea to have witness conferencing, or at any rate it has a significant downside that cannot be avoided.  For example, the procedure does not mix easily with video conferencing, where experts who are physically present have an advantage over those that are participating remotely.  On the other hand, if all experts participate by video link, it is very difficult to achieve the fluid communication that is the hallmark of witness conferencing when properly done.  That said, if a tribunal is determined to press ahead with the procedure, which is often the case, there is little counsel can do except prepare as best they can  -  and make sure their experts are prepared too. 

Advice for arbitrators

CIArb should be congratulated on producing a valuable resource for the whole arbitration community.   One key point that comes across clearly in the guidelines is the need for preparation in the part of the tribunal as well as counsel.  Parties are encouraged to produce a schedule of issues (points the experts cannot agree on) and an agreed chronology drafted specifically for the witness conference hearing.  However, there is no substitute for the tribunal reading all the key documents in a case rather than just the pleadings and the expert reports.  Another key point is that tribunals should be aware when witness conferencing is not working, and be ready to call a halt to the procedure when appropriate.  The guidelines flag both of these issues clearly.  In fact, the advice aimed at arbitrators is arguably the most valuable element of the guidelines.  It will be interesting to see to what extent it is followed.

Authors: Partners Maurice Kenton and Sapna Jhangiani and Professional Support Lawyer Giles Hutt


Stay up to date with Clyde & Co

Sign up to receive email updates straight to your inbox!