How to prove your case in a commercial dispute

In civil disputes a claim generally must be proven ‘on the balance of probabilities’ if it is to be successful. Our dispute specialists outline how to achieve this using written and oral evidence from witnesses and experts.

2 July 2021

A party making a claim bears the burden of proof, meaning that it is responsible for proving its claim. In civil disputes (as opposed to criminal matters) a claim generally must be proven ‘on the balance of probabilities’ if it is to be successful. How is this achieved?

The answer is that the claimant must present sufficient evidence to persuade the decision maker that its case is more probable than not. That is likely to require the factual evidence of witnesses directly involved in the relevant events (and supporting documentation, which those witnesses will speak to), and the opinion evidence of suitably qualified subject experts. 

Whether or not the evidence presented is effective in persuading the decision maker can sometimes depend as much on how it is presented as on its content. A recent case in the Technology and Construction Court - Cartwright Pond Ltd v Wild [2021] EWHC 1600 (TCC) (“Cartwright”) - illustrates the harm that can be caused to a party’s position by unhelpful or poorly presented evidence. 

Oral witness evidence 

As put by the court in Carmarthenshire Council v Y [2017] EWHC 36 (Fam), [2017] 4 WLR 136, “The general rule is that oral evidence given under cross-examination is the gold standard because it reflects the long-established common law consensus that the best way of assessing the reliability of the evidence is by confronting the witness." The process of testing the evidence of a witness will often shine a light on the strengths and the weaknesses of a case. If that evidence survives that process unscathed, it is likely to influence the outcome.

However, a weakness of witness evidence can be the “inherent unreliability of memory” (as put by the court in the recent case Naziyah Ismail v Ciaran Joyce [2020] EWHC 3453 (QB)). Witness evidence may be heard several years after the relevant events. Even if a witness has every intention of giving true answers, it is very possible that recollections have changed over time. A decision maker will be alive to this possibility, particularly where the witness’s version of events is not corroborated by documents or other witnesses. 

Another potential weakness can arise when a witness is particularly invested in a case, such that the witness’s perception of events is affected. In Cartwright, the defendant was being sued by a builder who had carried out works at the defendant’s home. The court found that the defendant “had clearly convinced herself that she was the wronged party throughout”. As a result, the court declined to rely on the defendant’s uncorroborated oral evidence. There was no suggestion of dishonesty. 

Thus a decision maker will interrogate witness evidence rather than simply taking it at face value. If corroborating evidence is available – for example, contemporaneous records that align with a witness’s account – that is likely to add weight to it. 

Written witness statements

An efficient way to present complex witness evidence may be to use written witness statements, which are permitted in many dispute resolution processes. 

A problem can arise when a statement is edited (typically by a legal representative) to such an extent that it is not the true evidence of the witness. Guidance published by the Commercial Court of the Scottish Court of Session states: “Words should not be put into a witness’s mouth. If a party produces such a document as the evidence of the witness, it is likely that it will receive little weight from the court and it may in some circumstances significantly damage a party’s case.”

For English disputes litigated in the Business and Property Courts, Practice Direction 57AC3 (which came into force in April 2021) goes further. It states requirements as to the content of witness statements and requires production of a statement of truth (signed by the witness) and certificate of compliance (signed by the legal representative). Sanctions can be imposed for non-compliance. 

An example of this problem can be seen in Cartwright, in which the court commented that the claimant’s main witness had seemingly “signed up to sections of his witness statement which rather overstated his true evidence”. As a result, the witness’s written statement was not reliable.

Some dispute resolution processes (such as adjudication) do not have prescriptive rules for evidence generally nor for the production or form of witness statements specifically. Indeed, the practice in adjudication has been to accord lower significance to the burden of proof. Nevertheless, when presenting evidence in these other processes, it is good practice to ensure that witness statements are the witness’s own evidence and are in the witness’s own words. Otherwise, they may be given little weight.

Expert evidence

A party’s position may be bolstered by the supportive opinion of a relevant subject expert (or, conversely, weakened by an unsupportive opinion). Who counts as an expert, and what evidence can be given by such a person, is the subject of detailed case law (and is outside the scope of this article). 

In litigation (and other dispute resolution processes) there are rules as to the particular procedure to be followed by a party wishing to rely upon expert evidence. Failure to follow the required steps can cause significant problems. For example, in Cartwright the defendant produced a supportive schedule prepared by a quantity surveyor, but failed to seek permission to rely upon the schedule as expert evidence. As such, the court said, “the contents of the schedule do not amount to evidence in their own right but simply as a statement of the defendant’s case.” Had the defendant complied with the correct procedural steps, the court may have placed more weight on the quantity surveyor’s findings. 

Input from a relevant expert is often expensive to obtain. To prevent this cost being wasted, parties should be careful to ensure compliance with all relevant rules and requirements.


The above examples illustrate the importance of fully considering the evidence to be presented in a commercial dispute. Some particular points to note are:

  • The evidence of a factual witness is likely to hold more weight if corroborated by documentation or other witness evidence.
  • Written witness statements should be the true evidence of the witness, not the words of a party’s representative. 
  • Where expert evidence is presented, care must be taken to ensure that the relevant procedural requirements are met. 

Cartwright and other case law demonstrates the harm that can be caused to a party’s case by poorly presented or unreliable evidence. To succeed in a commercial dispute, parties should endeavour to avoid these pitfalls. 

For more information please contact Iain Drummond, Partner, or Eilidh Dobson, Solicitor, of our property and infrastucture disputes team.