Hot tubs are not usually associated with the provision of expert evidence in court or arbitration proceedings, but the practice of expert witnesses testifying at the same time (concurrently, or in the ‘hot tub’) has been in place in Australia for several decades, and has found some limited favor in U.S. federal courts.[1] The practice is entrenched in court rules and practice notes in multiple Australian jurisdictions, including the Federal Court,[2] and has been increasingly taken up in other jurisdictions such as Canada, the U.K., Singapore, and New Zealand, as well as in international arbitrations. So, what is it, how does it work, and is it compatible with fundamental principles of American litigation?[3]

A flexible process

Wherever it has been used, the process of concurrent expert evidence has been flexible, and the contours of it differ from case to case. The trial judge retains discretion as to how the process will work, but it will typically involve the usual pre-trial disclosures, including expert reports, followed by a pre-trial expert conference (or ‘conclave’), the provision of a joint report, and then oral testimony from the experts, delivered together in the ‘hot tub’ or via a mix of solo and concurrent testimony. The process requires full participation of all parties to be effective as a tool to “enhance the efficiency, accuracy and ideally collegiality of the expert evidence process.”[4]

Pre-trial expert conference

The process typically commences in the traditional manner – experts exchange reports, followed by a series of rebuttals and replies. The experts then meet in a pre-trial conference to identify the areas in which they agree and disagree, the latter to be the focus of oral testimony at trial. Lawyers are not usually permitted to attend the conference, and experts are occasionally sequestered until the joint report is finalized. Discussions in this forum are robust. Although the experts will usually ‘agree to disagree’ on many matters, the process can be extremely useful in narrowing the issues in dispute and provides the experts with a unique opportunity to understand where they have fundamental differences of opinion, and where their opinions might diverge for other reasons such as contrary assumptions.

While the pre-trial conclave is not designed for any expert to strong-arm other participants in the process, lawyers for both parties will carefully prepare their experts for the conference. The experts must attend ready to argue their positions; the discussions are not usually privileged from subsequent disclosure, and a concession by an expert during the conclave can have ramifications for a case (for example, if an expert testified in open court as to an unhelpful comment made by another expert during the conclave, that could be damaging even if the comment is inadmissible hearsay).

Preparation of a joint report

An especially useful part of the process is the preparation of a joint report following the expert conclave. The areas of agreement and disagreement between the experts are documented in a draft report usually prepared by one expert and circulated amongst the other experts for input. The report will be structured according to key topics for expert evidence, and the judge will often be involved in identifying and defining the topics with the parties. The process of swapping drafts of the joint report continues until each party is satisfied that the report satisfactorily describes the areas of agreement and disagreement.

When prepared well, the joint report is an extremely effective method of highlighting the areas where opinions actually differ and allows the court to ensure the focus at trial is on only the areas of continuing disagreement between the experts. Experts can be surprised to find that the true areas of disagreement are very limited. By highlighting where the true debate lies, the joint report also has the potential to significantly reduce the amount of time the experts are required to prepare for and testify at trial. The joint report can also be a very effective tool in settlement negotiations.

Concurrent testimony at trial

At trial, experts testifying concurrently sit together for the duration of the concurrent session(s). Matters of practicality are key – is there enough room for everyone and their materials? How many microphones are available? Who sits closest to the Judge? The matter of space is particularly relevant when there are many experts giving evidence concurrently. At times the witness box is abandoned for more spacious areas of the courtroom, such as the jury box for a bench trial.

Lawyers for each party will lead evidence from their expert, which is sometimes undertaken by way of opening statements from each expert, and the parties will then ‘cross examine’ the experts. The process can differ between jurisdictions and depending upon the directions of the relevant court. For example, in the U.K., court rules provide that ordinarily “the judge will initiate the discussion by asking the experts, in turn, for their views in relation to the issues on the agenda. 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.”[5] Questioning of the experts is structured around the topics identified through the joint report process, and each expert will testify concerning a particular topic before the court moves on to the next topic. The experts can be asked to comment on evidence given by other experts and are free to ask each other questions. In this way, the various opinions can be lined up against each other in real time, and questions can be directed by the judge or by counsel to understand the impact of assumptions on the various opinions.

The process is much more conversational than a typical cross examination by an adversary’s counsel, with the judge taking an active role, and generally chairing the discussion. Some lawyers lament the partial loss of control over the process, and view it as diluting the adversarial nature of a trial, by imposing inquisitorial elements controlled by the judge with limited influence of the parties.

Experts however can find this atmosphere makes the process of testifying much less daunting than ordinary cross-examination. Expert witnesses have anecdotally commented that part of the effectiveness of the process is that it removes the “lawyer filter,” and allows experts to more effectively explain highly technical issues in simple terms. Experts also emphasize the critical importance of ensuring the expert witness has an appropriate personality for the process – and that they will be on equal footing to opposing experts. More experienced experts often perform better in the hot tub, particularly if facing highly regarded experts in their field with intimidating reputations.

Does concurrent evidence have a place in American litigation?

Although other jurisdictions specifically provide for it in procedural rules, in the U.S. concurrent evidence is not specifically dealt with in the Federal Rules of Civil Procedure or Federal Rules of Evidence. However, district court judges are empowered to “exercise reasonable control over the mode and order of examining witnesses and presenting evidence,” including to “avoid wasting time,”[6] and can call and examine witnesses.[7] The Federal Rules of Civil Procedure themselves should be “construed, administered, and employed by the court and the parties to secure the just, speedy, and inexpensive determination of every action and proceeding.”[8] The process has generally been viewed as consistent with both sets of rules.[9]

For lawyers practicing in the U.S., the process may be viewed as diluting the expert’s role as advocate, and limiting the ability of counsel to effectively cross examine other parties’ experts. In Australia, the Judge’s active role provides a valuable reminder to the experts that they have an overriding duty to the court, in the same way that Australian lawyers owe a duty to the court, and assists the Court to understand the key issues by controlling the agenda for the discussion. This duty to the court is a significant difference between the expert’s role and function in litigation in Australia and the U.S. and is one reason why the Australian system might lend itself more readily to the expert conclave process.

Whether the use of expert evidence will dilute his/her role as advocate will be a product of how the process is applied, and some of the concerns can be met by the parties’ retaining rights to challenge the admissibility of evidence or conduct a further cross examination. Despite some concerns, the process has found favor in various U.S. jurisdictions which otherwise have strong adversarial traditions in litigation. Hot tubbing has been viewed as potentially playing a useful role at several stages of U.S. litigation, including joint expert conferences, depositions, Daubert hearings, summary judgment hearings, class certification hearings, injunction requests, judge-alone trials and potentially jury trials, as well as settlement negotiations.[10] Outside the U.S., the process has been overwhelmingly used as a tool in bench trials. Given the prevalence of jury trials in the U.S., there is a real question over the extent to which the process might find favor in jury trials.

Concurrent expert evidence as a useful tool

Concurrent expert evidence can be a very effective time saver before and at trial, which is an increasing concern of judges and clients seeking to reduce the time and costs associated with litigation. Furthermore, judges in Australia and the U.S. have viewed the process as more effective overall as a learning tool for key issues in complex or technical litigation than traditional methods of expert evidence.[11]

From the expert’s perspective, the concurrent expert evidence process is viewed by many experts as giving them the best opportunity to ensure their key points are made; they are not constrained by the questioning of their cross-examiner and have more freedom to explain their opinions. Personality differences do create fears that the court will defer to the most forceful speaker, but such concerns can be effectively managed by the judge, who can ensure that an impartial and objective view of the evidence is taken regardless of its form, and can order an associate judge or master to supervise the process.

The process can result in a much more streamlined expert evidence process and can allow the parties and the court to focus on the real issues in dispute, both in settlement negotiations and at trial. Concurrent expert evidence will not be appropriate in many cases, and it has rarely if ever been used in a jury case, but it is a potentially effective tool that parties to litigation in the U.S. should consider.

This article was first published in the IBA Litigation Committee newsletter in September 2019, and is reproduced by kind permission of the International Bar Association, London, UK. © International Bar Association.