The Impersistence of Memory - Fact Witness Evidence in International Arbitration

Fact witness evidence is a common feature of international arbitration and other forms of formal dispute resolution. A study by the ICC Commission has revealed that human memory is fragile, malleable and may become unwittingly corrupted. In complex construction engineering disputes, what can be done to ensure memory is reliable?

Evidence in international arbitration, particularly in complex construction engineering cases, is usually derived from three primary sources:

  1. Contemporaneous documents, which include documents forming the project record such as e-mails, letters, reports, drawings, photographs, notices, etc., but also documents created by individuals and not necessarily stored in the project files. This may include e-mails sent from private accounts, text messages, handwritten notes and diary entries.
  2. Expert evidence, which is commonly used to give expert opinion to the tribunal on technical matters such as schedule delay analysis, quantum, or evidence in particular technical disciplines such as structural engineering, acoustic engineering or project management.
  3. Fact witness evidence, which is testimony given by those persons with experience of the contemporaneous events as they occurred on the project. With the assistance of lawyers, fact witnesses produce a written witness statement detailing their recollection of the events. The witness may be subject to cross-examination at a hearing by the opponent’s counsel on the content of the statement. The tribunal itself may also ask the witness questions directly.

Fact witness evidence does not have to form part of international arbitration, but it typically does. It will generally form part of the procedural order for the case. Parties submit fact witness evidence to prove disputed facts that are unsupported by documents and/or where a witness is required to testify to the facts contained in documents, or explain the background behind the creation of those documents. Fact witness evidence can bring many benefits to a case—a credible, honest and genuine fact witness may come across well before the tribunal. The individual can sometimes better explain the motives of the claimant or defendant for taking particular decisions or actions in relation to the events that occurred. Any individual working on a particular project may, at least in theory, be called to give fact evidence. The majority of people will never do this in their lives, but in construction engineering projects some will, particularly those in prominent ‘on the ground’ roles such as project managers, engineering managers and construction managers. While many find this experience daunting, particularly the prospect of cross-examination, the fact witness is not responsible for winning or losing a case. Fact witnesses just need to explain the facts. That sounds simple enough, but fact witnesses can feel under pressure to try to remember everything that happened on the project. It is best recognising the impossibility of this task. In construction engineering projects, particularly large scale or mega projects, the events on which a fact witness is called to give evidence may have taken place many years earlier, in which time the witness has moved on to other roles or different projects. Anyone who has struggled to recall what they did last week (as happens to this author from time to time) knows it is not possible for a fact witness to recall everything that happened on a complex project that occurred several years previously. A 2020 report by the ICC Commission, “The Accuracy of Fact Witness Memory in International Arbitration” explored the science of human memory in terms of arbitral practice. This study revealed that human memory was fragile, malleable and that memories could become unwittingly corrupted. The report explained that memories could easily become distorted and that even an honest witness may be less reliable than expected if memory distortion occurs. Potentially most alarmingly was that scientific studies have shown it is possible that misinformation (i.e. manufactured evidence) can be used to plant false memories. The report advocates better awareness of the circumstances in which memories may become distorted and proposes steps that may be taken by witnesses, counsel and tribunals to reduce the risk of memory distortion.


The most practical step is an obvious one. We always advocate that parties involved in engineering construction projects should aim to keep as full, detailed and well-ordered records of the project as possible. Contemporaneous evidence is vital in proving a claim or successfully defending one. For example, in one case, in the absence of any real documentary evidence from the other party to support a delay claim, our client’s schedule delay expert was able to provide persuasive counterevidence by a delay analysis compiled with the help of detailed handwritten records kept by our client (the employer).Keeping contemporaneous documents is a sensible measure to counter possible memory distortion. If a fact witness is able to rely on documents as an aide memoire rather than purely their own recollections, this would seem to reduce the prospect of memory distortion.While it is impossible to document everything that happens on a complex engineering construction project that may run for several years, the parties and individuals involved should consider ways of keeping their own records at least of key events. Photography and video are obvious and accessible examples in addition to written records. This may form valuable contemporaneous evidence in itself as well as help to guard against potential distortion of memories should individuals be called upon to act as a fact witness.


The content of this page is a summary of the law in force at the date of publication and is not exhaustive, nor does it contain definitive advice. Specialist legal advice should be sought in relation to any queries that may arise.

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