Hot-tubbing, or concurrent evidence, is a tool that allows experts to tell the court how it is without being cross-examined. Charles Blamire-Brown looks at the pros and cons

Gone are the days when parties’ expert witnesses take it in turns to be examined, then re-examined in the dock while the judge or arbitrator sits passively listening. Hot-tubbing has arrived - to an extent. But is this welcome news?

Hot-tubbing, or “concurrent evidence” as it is otherwise known, involves both parties’ experts sitting in the box with the judge or arbitrator leading a discussion between them. This is a discussion, not a cross-examination. There are no barristers shaping the way the experts give their evidence. The principle is that the experts can tell it how it is.

In the hot-tub, the experts can talk between themselves and ask questions of each other. The judge or arbitrator takes the lead as inquisitor directing questions to both experts and skipping the middleman.

However, using concurrent expert evidence is voluntary, and requires full agreement from all parties.

In an open and frank discussion, the idea is that the experts are more likely to make concessions and come to agreement on common issues. The judge or arbitrator is also able to get to the root of the issues in a much more efficient manner by asking the experts direct questions. The risk of an expert giving an unclear or confusing answer is reduced by the opportunity for this to be immediately challenged by someone who has the technical expertise to challenge them. This will bring substantial savings in time and costs, or so the theory goes.

The hot-tub principle has been around in arbitration in various guises for a while. It is commonly used after cross-examination. However, arbitrators are sometimes reluctant
to embrace this interactive forum for fear of being criticised by the parties for breaching the arbitrator’s duty to act fairly and to give each party an opportunity to put their case forward.

Indeed, the hot-tub principle may appear to contravene these fundamental principles behind arbitration. In circumstances where one party’s expert is a strong advocate, how can it be said that the party with a less bullish expert has had a fair opportunity to present its case unobstructed from interruption?  In adopting an inquisitorial approach, the arbitrator may be tempted to find arguments to support their pre-formed views as to the nature of the parties’ cases. But how is this necessarily acting fairly between the parties?

The hot-tub certainly places far more importance on the need for experts to be good advocates. But is this not a dilution of the expert’s proper role? Experts are used by the tribunal precisely to be experts. They are not silver-tongued barristers - it is their knowledge and expertise that should carry the most weight.

The risk of an expert giving an unclear or confusing answer is reduced by the opportunity for this to be immediately challenged

The major concern for the parties in opting to use concurrent evidence is losing the control and platform to present their case that traditional methods of cross-examination and
re-examination afford. However, this can be reduced by effectively preparing experts for the hot-tub, or by selecting an expert with experience of this format. Presently, concurrent evidence is used in arbitration, but Lord Jackson, in carrying out his recent review into the costs of litigation, has recommended its use in the court process. Based on this review, the Technology and Construction Court includes reference to hot-tubbing in its latest procedural guide, which came out last month. The TCC in Manchester is the first court brave enough to take the plunge.

It remains to be seen whether hot-tubbing will lead to a reduction in costs, both in litigation and in arbitration. If parties simply opt for both the hot-tub and usual methods of cross examination, then it is unlikely that the amount of time saved will be significant.

For hot-tubbing to be successful, parties, including arbitrators and judges, will need to properly embrace the purpose of the hot-tub: to get to the nub of the issues between the parties in a constructive rather than combative manner. However, the effectiveness and fair operation of this procedure is dependent on the tribunal’s approach and ability to effectively manage the process.

Charles Blamire-Brown is an associate at Pinsent Masons