‘Hot tubbing’– or ‘concurrent evidence’ as it is more formally known, is a means of eliciting expert evidence at trial, whereby the expert witnesses give their evidence in chief together and by engaging in discussion directly with the trial judge and each other. This approach is significantly different from the traditional model of cross-examination, in which each expert is individually examined and then cross-examined by opposing counsel.
Australia was the first to introduce the practice into civil trials, however, hot-tubbing has since been successfully adopted in the UK and has become widely used in International Arbitration.
While there are no hard and fast rules for hot-tubbing, the general procedure is somewhat consistent across jurisdictions:
Prior to trial, the experts are required to prepare and exchange written reports. They will then meet, usually in the absence of counsel, to discuss their reports and prepare a joint statement. The purpose of the joint statement is to identify the specific points upon which the experts agree and disagree. The identified areas of disagreement are then used as the basis of an agenda for the ‘hot-tub’, which is prepared and agreed by the parties. This agenda is provided to the judge in advance of the trial. At trial the experts are sworn in together. The judge initiates and directs the discussion based on the agenda. Through their oral testimony, the experts will try to reconcile the areas of disagreement. Each of the experts is provided the opportunity to present their views and answer any questions posed by the other expert. If necessary, counsel is then permitted to ask questions of each of the experts. At the end, the judge will summarize the different positions put forth by each of the experts on the issues and get them to confirm or correct if the judge’s interpretation is incorrect.
By focusing only on areas of contention, particularly during cross-examination, there seems to be a significant reduction in the amount of time required to examine each expert. Overall, this can lead to time and cost savings and increase the overall efficiency of eliciting expert evidence at trial.
In Canada, the Federal Court Rules (the “FCR”) governing expert evidence were updated in 2010 to incorporate hot-tubbing. Paragraph 282.1 of the FCR now reads:
“The Court may require that some or all of the expert witnesses testify as a panel after the completion of the testimony of the non-expert witnesses of each party or at any other time that the Court may determine…
Expert witnesses shall give their views and may be directed to comment on the views of other panel members and to make concluding statements. With leave of the Court, they may pose questions to other panel members.”
In addition, a pretrial version of hot-tubbing was added to the Ontario Rules of Civil Procedure (the “Rules”) in 2010, and appears to be gaining traction. Pursuant to Rule 20.05(2)(k) of the Rules, the court may give direction or stipulate that experts meet on a without-prejudice basis before trial where:
“(i) there is a reasonable prospect for agreement on some or all of the issues, or
(ii) the rationale for opposing expert opinions is unknown and clarification on areas of disagreement would assist the parties or the court.”
This practice of hot-tubbing, both before trial and at trial, is becoming more widely used in an effort to reduce areas of disagreement between experts and to increase efficiency of facilitating settlements and assisting the court at trial.
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