‘Hot-Tubbing’ Expert Witnesses: An Experimental Technique From Australia Makes a Splash in U.S. Courts

Expert witness testimony in the U.S. is traditionally adversarial, but "hot-tubbing," a collaborative approach from Australia where experts discuss the case together with the judge, offers an alternative.

Hot Tubing Expert Witnesses

ByAnjelica Cappellino, J.D.


Updated on May 21, 2024

Hot Tubing Expert Witnesses

Expert witness testimony in the American judicial system has traditionally been extracted the same way every case; each side obtains and examines their own expert, with their own theories and conclusions, and each witness is then cross-examined by opposing counsel. This practice has long been recognized as the blueprint of expert testimony in the United States’ adversarial process. But this method is not the only approach to eliciting expert testimony.

What is "Hot-tubbing"?

Hot-tubbing,” also known as concurrent evidence, is a procedure whereby the experts of both parties convene with the judge and discuss the case together under oath in an attempt to reach an agreement. Ostensibly, hot-tubbing is meant to be less formalized and adversarial, with the ultimate goal being compromise between the parties.

This unique approach of soliciting expert witness testimony first garnered popularity in Australia, where the courts have utilized this method for over twenty years. Concurrent expert evidence originated in the Australian Competition Tribunal. Where it was used to receive evidence from economic experts, then branched out to other non-jury cases in the Australian courts. It is an established practice that is endorsed by a number of its jurisdictions and recognized in court rules and practice notes.

Hot-tubbing is characterized as a discussion among experts. Typically, the expert witness presents an opening statement and then engages in conversation with the judge and the other party’s expert. Prior to trial, experts each report to each other and both present a joint submission that outlines the points of agreement and disagreement. Because each party is aware of the other’s testimony prior to trial, objections by counsel are usually unnecessary. While cross-examination by trial counsel is permitted, lawyers do not play as central a role in extracting expert testimony; as all parties are expected and encouraged to discuss and question each other freely.

Last year, U.S. District Judge Jack Zouhary introduced the technique to resolve the question of class certification in an antitrust multi-district litigation and found the experience “rewarding,” noting that “[he] would not hesitate to use it again in the right case.”

But can hot-tubbing fit within the American judicial system? The biggest implication of concurrent evidence is that it limits cross-examination. As a traditionally adversarial system, American trials are rooted in the ability of both parties to extensively question the other. If hot-tubbing were ever to be introduced in the United States courts, it would be after a long examination of its positive and negative implications on the judicial system as a whole.

What are the Goals of Hot-Tubbing?

The main goal of hot-tubbing is to focus on the ultimate issues of fact in a more bipartisan atmosphere. Without the strictly adversarial process of direct- and cross-examination, experts are free to engage in discussions with each other that can lead to finding common ground on the issues and eliminating many perceived disagreements.

This helps alleviate confusion for the judge, jury, and potentially even the parties themselves.

Hot-tubbing also prevents credibility and factual accuracy being contingent upon an expert witness’ ability to relate to the fact-finder. Because complex, foreign matters, such as highly scientific information, may be difficult to understand, fact-finders can sometimes make decisions based on an expert’s demeanor, credentials, and presentation skills.

Hot tubbing is currently only employed in non-jury cases. However it is nonetheless important to note that judges may also gauge an expert’s demeanor when evaluating complicated testimony. Concurrent expert evidence diminishes the likelihood of such battles between witnesses by shifting the focus from an expert’s behavior on the stand to the actual information he is offering. Without the adversarial nature of extensive cross-examination, and with both experts aware of their points of agreement and disagreement beforehand, each witness has the potential to present their arguments in a less confrontational and more straightforward way. As Australian judge, Justice Peter McClellan of the Land and Environmental Court of New South Wales commented, “You can feel the release of the tension which normally infects the evidence-gathering process.”

Many proponents also argue that hot-tubbing reduces the opinion that expert witnesses are biased towards their own parties. By introducing concurrent evidence with “more input and assistance from the experts themselves in lieu of their, perhaps unfairly, perceived role as being inherently even if not consciously, biased to the case of the party calling them,” hot-tubbing allows the expert witnesses to take the reins of their own testimony. Hence, experts more personally control how the fact-finder perceives them in terms of credibility and impartiality.

Implications of Hot-Tubbing in the U.S.

While not usually a part of American jurisprudence, there are some courts in the United States that have tested the waters with concurrent expert evidence. For example, Judge David Laro, of the United States Tax Court, has previously utilized this method in Rovakat, LLC v. CIR, 102 T.C.M. (CCH) 264 (T.C. 2011), aff’d, 529 F. App’x 124 (3d Cir. 2013), in what appeared to be a successful elicitation of expert testimony. As the Judge Laro explains:

To implement the concurrent testimony, the Court sat at a large table in the middle of the courtroom with all three experts, each of whom was under oath. The parties’ counsel sat a few feet away. The Court then engaged the experts in a three-way conversation about ultimate issues of fact. Counsel could, but did not, object to any of the experts’ testimony. When necessary, the Court directed the discussion and focused on matters that the Court considered important to resolve. By engaging in this conversational testimony, the experts were able and allowed to speak to each other, to ask questions, and to probe weaknesses in any other expert’s testimony. The discussion that followed was highly focused, highly structured, and directed by the Court.

But can Australian evidentiary practice truly translate into American courts? After all, American jurisprudence is based on an adversarial system, which hot-tubbing seeks to moderate. As Joe Cecil of the Federal Judicial Center in Washington, D.C. notes, “Assuming the judge has an active interest in ferreting out the truth and the experts are candid, I prefer the hot-tubbing option…but those are two bold assumptions, and the procedure drives the attorneys nuts.”

Another consideration, both for and against concurrent evidence, is that the control of the witness is out of the attorneys’ hands. Attorneys would have to extensively prepare their witnesses not just for the adversary’s cross-examination but also any questions that can be directly fielded by the adversary’s expert. Furthermore, in such an open forum, trial lawyers lose control over what evidence is before the court if the discussions between the experts veer off the attorney’s planned narrative.

Whether hot-tubbing catches on in the United States is yet to be seen; as it would change an evidentiary practice deeply rooted in the adversarial system. But while it will never replace our current system, hot-tubbing may certainly become an occasionally utilized alternative in the right circumstances.

About the author

Anjelica Cappellino, J.D.

Anjelica Cappellino, J.D.

Anjelica Cappellino, Esq., a New York Law School alumna and psychology graduate from St. John’s University, is an accomplished attorney at Meringolo & Associates, P.C. She specializes in federal criminal defense and civil litigation, with significant experience in high-profile cases across New York’s Southern and Eastern Districts. Her notable work includes involvement in complex cases such as United States v. Joseph Merlino, related to racketeering, and U.S. v. Jimmy Cournoyer, concerning drug trafficking and criminal enterprise.

Ms. Cappellino has effectively represented clients in sentencing preparations, often achieving reduced sentences. She has also actively participated in federal civil litigation, showcasing her diverse legal skill set. Her co-authored article in the Albany Law Review on the Federal Sentencing Guidelines underscores her deep understanding of federal sentencing and its legal nuances. Cappellino's expertise in both trial and litigation marks her as a proficient attorney in federal criminal and civil law.

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