All in together

At the end of 2016, Lord Woolman issued his decision in SSE Generation Ltd v Hochtief Solutions AG [2016] CSOH 177. The case concerned liability for the collapse of part of a water-bearing tunnel at Glendoe hydroelectric station in Fort Augustus.

This was one of the longest and most technically complex cases to come before the Scottish courts in recent years. The court sat for 91 days; 73,000 documents were lodged, including 37 expert reports and 91 witness statements. Of those, 19 experts gave evidence at proof, and 46 witnesses of fact.

The court was faced with the challenge of hearing and comprehending technically difficult expert evidence on matters such as structural geology, rock mechanics and tunnel engineering.

The case was the first in the Court of Session to use “hot-tubbing” to hear expert evidence. Hot-tubbing, or concurrent evidence, is a process whereby expert witnesses of the same or similar disciplines give their evidence at the same time in a structured discussion, with the judge acting as chairperson.

Concurrent expert evidence is already a feature of civil litigation in England, with a suggested procedure set out in Practice Direction 35, supplementing the Civil Procedure Rules, Part 35. It is also commonly used in arbitration and other forms of ADR. So what does it entail?

Views from experience

The procedure adopted by Lord Woolman mirrored that set down in Practice Direction 35. His Lordship was also guided by video demonstrations from the Judicial Committee of the New South Wales Commission. It was essentially this:

• Counsel for the parties agreed in advance a list of suggested topics to be discussed during the concurrent evidence session.
• Lord Woolman initiated the discussion between the expert witnesses by asking one of them to set out his position on a particular issue, then inviting the others to participate in the discussion, questioning one another as appropriate.
• Counsel were invited to ask follow-up questions.

A 2016 report by the Civil Justice Council on hot-tubbing (read the report online), found the procedure is well liked by judges and practitioners alike. This view was echoed by Lord Woolman in his judgment at para 258: “I found it an extremely valuable exercise and one which I would repeat in suitable future cases. Instead of hearing complex testimony weeks apart, I was able to hear the different opinions at one and the same time. They were also able to challenge one another’s position. This brought the topics into sharp focus. Each expert had to crystallise his position.”

When considering the CJC’s report, the English Civil Procedure Rule Committee expressed some caution over the use of hot-tubbing. It noted that hot-tubbing required significant work and time, and early buy-in of all concerned. It was also felt that if hot-tubbing is used, there must be adequate safeguards in place to ensure fairness of the proceedings.

This was achieved in SSE v Hochtief by using hot-tubbing in addition to, and not instead of cross-examination, so both parties had sufficient opportunity to test the experts’ evidence. By hearing evidence concurrently, it was possible to focus the key issues and garner the respective positions of the experts on those issues.

Conditions for success

There are two major factors that will determine the success of hot-tubbing:

• Is the case suitable? Lord Woolman commented that the process was most useful where there was a narrow technical dispute – less so where there was little common ground between the parties or the level of detail was too great.
• Does the process have the support of all involved? Litigants will need to be comfortable with novel approaches to taking evidence. Expert witnesses need to understand the process and be confident asking and answering questions of one another. Solicitors and advocates will have to agree a procedure up front, and possibly an agenda of topics to be discussed. And finally, judges need to be fully engaged with the case in order to formulate suitable questions and chair a productive discussion.

Provided these criteria are met, there is no reason why hot-tubbing should not be used more widely. The opportunity for experts to discuss and question one another is a useful addition to the examination process. This interactive process is likely to crystallise positions, and highlight areas of agreement or divergence of expert opinion. Ideally, this will lead to more measured and reasonable positions being advanced, and ease the decision-making process.