News Update Arbitration

The ICC Report on the Accuracy of Fact Witness Memory in International Arbitration
17 februari 2021
17 February 2021

On 19 January 2021, the ICC Task Force on Maximising the Probative Value of Witness Evidence (the "Task Force") presented its report on the accuracy of fact witness memory in international arbitration (the "Report"). The Report analyses the psychological science of human memory and aims to guide counsel and arbitrators on how to increase the evidentiary value of witness evidence, considering the functioning of human memory. This News Update gives a high-level overview of the Report's contents and key findings.


Witness evidence remains a relevant source of information in international arbitration because it may be decisive for a tribunal to reach a decision in a case. At the same time, preparing witness statements and presenting oral witness evidence is often time-consuming and costly, which all goes to waste if the witness evidence loses credibility.

Witness memory is imperfect by nature and many stimuli may influence memory. The Report explores general ways in which these influences, or distortions, may be diminished to enhance the evidentiary value of witness evidence. Furthermore, the Task Force examined how participants in arbitral proceedings may contribute to reducing distortions in a witness's memory.


The Report is divided into six sections, together with two appendices, setting out scientific research conducted by two scientists on human memory, with a particular focus on different facets of witness evidence. Section II of the Report describes the research conducted and sets out the conclusions reached by these two scientists. Section III then provides an empirical analysis of whether witness evidence may be affected similarly to the way it may be influenced in other contexts. Consequently, based on this empirical data, the Report concludes that flawed memory also occurs in the type of commercial setting that is typical in arbitration proceedings. Section IV subsequently deals with how witness evidence is used in international arbitration. Among other things, this section examines when witness memory may or may not be significant given that concerns about memory distortion are only relevant when the witness's exact memory is required.


In Section V, the Report sets out suggestions for in-house and external counsel and arbitral tribunals to reduce the risk of memory distortion and improve the credibility of witness evidence.

For example, the Report suggests that counsel meet with potential witnesses individually rather than in groups, to diminish memory contamination. Additionally, it recommends that the arbitral tribunal discuss the possibility of witness evidence at the beginning of the arbitral proceedings and by giving clear instructions to the witness prior to its examination. This way, the arbitral tribunal could reduce any witness memory distortions.

Importantly, the Report underlines that its suggestions should not be considered as mandatory. Instead, appropriate steps should be assessed on a case-by-case basis, particularly for the following two reasons:
  1. witness evidence may take on different roles in arbitration and is not always dependent on accurate memory; and
  2. there are several other considerations that should be considered when trying to reduce the risk of memory distortions, which will not necessarily require taking the steps provided in Section V. For example, exposing a witness to post-event information may change the witness's memories. At the same time, being exposed to this information may refresh the witness' memory. Accordingly, the evidence presented by the witness may be more consistent and complete. In any event, the specifics of each case should guide what steps should be taken to diminish memory distortions.
    According to the Task Force, it is important that counsel, including in-house counsel, and arbitrators are aware of how the human memory functions. Therefore, it for instance recommends that counsel, including in-house counsel, and arbitrators are trained by psychologists. Increasing awareness will be a key step forward for all participants in the arbitration process.

    Lastly, the Report emphasises that the witness's evidentiary value should be considered equal to the value of evidence, and that witness evidence should not be categorised as 'second best'. The Report instead aims to reduce concerns that could lead to documentary evidence being preferred over witness evidence.

    The Report comes as a welcome contribution broadening understanding on how fact witness memory functions and highlighting the importance of witness evidence in international arbitration. This Report will likely become a useful guide on the issue, to be used by arbitration practitioners on a regular basis.
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