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CIArb launches guidelines for witness conferencing in international arbitration

6 May 2019

The Chartered Institute of Arbitrators (“CIArb”) has recently launched its Guidelines for Witness Conferencing in International Arbitration (“Guidelines”) in Singapore. The Guidelines aim to assist parties, arbitrators and experts in the preparation for and presentation of evidence during Witness Conferencing.

Witness Conferencing

Witness Conferencing (or colloquially, “hot-tubbing”) is a means of adducing evidence whereby two or more witnesses give evidence concurrently before a tribunal. This is in contrast to the traditional method of cross-examination, in which evidence is adduced through the examination of witnesses consecutively, and with parties’ counsel playing a predominant role in the asking of questions. 

Unlike in traditional cross-examination, Witness Conferencing allows the witnesses and the tribunal to exert greater control during the proceedings. It also allows witnesses to interact with each other in a way which will not occur under traditional cross-examination. 

Witness Conferencing has been generally well-received, in both litigation and arbitration proceedings across many jurisdictions, and in particular for the taking of opinion evidence from expert witnesses. As stated in the Preamble to the Guidelines, the popularity of Witness Conferencing is attributed to the following perceived advantages: 

  • Side-by-side presentation of evidence makes it easier to compare witnesses’ different views on an issue, and for the witnesses to challenge each other’s views with direct responses or rebuttals. 
  • Improved quality of evidence: Expert witnesses may be less willing to make technically incorrect assertions in front of a peer who can supply an immediate rebuttal.
  • Promotes efficiency: Tribunal can hear evidence from all the witnesses on the issues at once, rather than at different stages of a hearing.

However, parties and the tribunal need to be aware of the dynamics between witnesses, such as existing unfriendliness or hostility that may impede the presentation of evidence. The presence of multiple witnesses also generates more unpredictability, and potentially a greater need for the tribunal to intervene than in traditional cross examination. 

The Guidelines were therefore conceived to provide guidance for counsel and arbitrators on whether a Witness Conference should even be considered. 


The Guidelines consist of 3 main sections. 

Firstly, there is a non-exhaustive Checklist of matters for parties to consider in determining whether to even conduct a Witness Conference.

The second section is a set of Standard Directions providing a general framework for witness conferencing to be eventually incorporated as part of an initial procedural order. Subsequently, the tribunal can then issue Specific Directions on the holding of a Witness Conference once the issues and identities of the witnesses have crystallized.

Crucially, the Standard Directions merely confirms that the tribunal may take concurrent evidence in relation to issues as it considers appropriate; it does not preclude the taking of consecutive evidence from the same or other witnesses on other issues. 

Third, the Guidelines provide for the issue of Specific Directions once the parties have determined to hold a Witness Conference. 3 possible procedural frameworks are provided: 

  • Tribunal-led conference: Similar to the inquisitorial approach in civil law systems, the tribunal guides the questioning of the witnesses;
  • Witness-led conference: The witnesses themselves lead the conference, with minimal input from counsel or the tribunal;
  • Counsel-led conference: Each party’s counsel questions the opposing party’s witness, but may invite their own party’s witness to respond to the opposing witness’s answers. 

It is open for the parties to combine the above approaches to suit the case at hand. Multiple Witness Conferences could also be held for the different issues and types of witnesses involved. 

Whichever approach is adopted, it is provided that the tribunal maintains ultimate control of the procedure and should adjust the process as the conference progresses. 


Prior to the Guidelines, there has been a dearth of supporting materials on Witness Conferencing in international arbitration proceedings. It is envisaged that the Guidelines will serve as a useful framework for tribunals and parties to consider Witness Conferencing. 

At the same time, the Guidelines recognize the inherent flexibility required for Witness Conferencing, and have therefore provided for a multitude of approaches for parties to adopt accordingly.