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December 2013
Number 1

Will it all come out in the wash?

"Hot-Tubbing" for experts


One of the new features of the changes to the Civil Procedure Rules, which govern the way experts give evidence in England and Wales, was the introduction of concurrent evidence. This practice, described in CPR Practice direction 35 at paragraph 11.1 and known colloquially as "hot-tubbing" (but having nothing to do with the various interweb sites dedicated to less professional aims) has been available in other commonwealth jurisdictions for some years. It is an interesting innovation - and one which all experts must be familiar with since it is likely to become far more common than conventional evidence at trial.

Hot-tubbing can take place at any stage of the litigation process after a claim form has been issued. It follows that a judge may order experts to get into the hot-tub during the interlocutory stages as well as in a trial. And, rather than each expert being individually cross-examined on their evidence by counsel, the process is led by the judge, who questions the experts directly. Counsel may ask questions at the end.

The rules state that:

  • (1) 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 that expert's own questions of the first expert;
  • (2) after the process set out in (1) 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; and
  • (3) after the process set out in (2) has been completed, the judge may summarise the experts' different positions on the issue and ask them to confirm or correct that summary. Concurrent evidence has been found to be useful when there are numerous points in dispute, but it can equally well be used when there is a central issue to be decided by the judge. It can be used to clarify or limit matters to be tried - or to refine issues ready for mediation or settlement meetings. The idea is that it continues the transformation of an expert from that of "hired gun" to "judicial adviser" begun with the 1998 Rules. The hot-tub should result in the judge being clearer more quickly and more directly about the evidence or opinions that are on offer. For the expert, the experience should be akin to a viva.

Concurrent evidence allows the judge to hear each expert's evidence on each point in dispute at the same time, thereby allowing them to more easily weigh up the evidence. Each expert can comment on the other's evidence, giving them the opportunity to bring out weaknesses in the other's arguments, point out factual inaccuracies and challenge unsound opinions.

The absence of adversarial questioning means that experts are much more involved, and can clarify and explain the issues in dispute more clearly, making them more likely to get their opinion across to a judge. They do not need to defend a position but rather assist the judge to understand. Counsel may clarify what has been said but should not obfuscate.


The Rules envisage the judge setting an agenda to discuss the issues in dispute, which will be promulgated in advance, to allow the experts to prepare. The expert evidence given should be far more focused than that in adversarial contests and take less time. It should accordingly be welcomed by experts as an extension of professionalism and a reduction of the risk of being engaged in hostile encounters with barristers.

But, and it is an important caveat - the experts must be prepared for this process. Training, such as that which is available on the SpecialistInfo "Advanced" and "Court Room Skills" courses, is strongly recommended for all experts who may face this process. Solicitors are likely to want the assurance that experts know how to operate in a concurrent evidence environment - and that they appreciate the challenges and opportunities that it presents.

Finally - it must also be remembered that the hot-tub does not spell the ending of court-room evidence. Where there are important issues, and where it is right that an opinion should be open to challenge, then experts will continue to go to court. When they do, the circumstances are likely to be more, rather than less, challenging for the uninitiated and once again, without adequate training, experts will find the hair-dryer treatment waiting for those who have let it all come out in the wash

By Jonathan Dingle, Barrister-at-Law of 218 Strand and a leader on Specialist Info medico-legal courses.