Expert witness evidence is a significant factor in the outcome of construction disputes. A construction litigator may have to become familiar with the evidence of experts in a variety of fields in order to establish an accurate picture of what went wrong, what delay or disruption this caused, and how much it will cost to fix the issue. Experts in delay analysis are key when it comes to determining entitlement to extensions of time or loss and expense.

When hearing the evidence of a delay expert, a judge may be presented with two (or more) competing perspectives. Even when used to dealing with similar disputes, it is undoubtedly difficult to determine which view of several well-qualified individuals should be preferred. Finding ways to assess these different opinions is therefore of great utility in assisting a judge to come to a decision. On the other side, parties to a dispute would be well advised to keep on top of the ways in which a judge will compare the evidence before them, as this should inform their choice of expert.

Thomas Barnes & Sons Plc (In Administration) v Blackburn with Darwen Borough Council

This case concerned the construction of Blackburn Bus Station for which the Council chose Thomas Barnes & Sons as main contractor.

The Council terminated the contract for alleged default by Barnes before the work was completed. Barnes claimed that the Council's refusal to make interim payments and the subsequent termination were responsible for Barnes going into administration. Barnes' administrators sought money due on a proper valuation of the work done at the date of termination including claims for loss and expense as a result of the prolongation of the contract works purportedly caused by the Council. In deciding the case, a finding of which issues were the cause of the delay was crucial.

The case is helpful in that it gives some indication of how a court might assess competing approaches to delay analysis adopted by expert witnesses.

The use of the SCL Delay and Disruption Protocol was key in the evidence of both sides' expert witnesses.

The protocol is intended to provide guidance to assist in determining delay and disruption issues that commonly arise in construction projects, with the intention of allowing parties to a construction contract to avoid unnecessary disputes. Part of the protocol provides guidance on delay analysis carried out some time after the effect of the event that caused delay. The protocol lists six commonly used methods of delay analysis and describes their use, advantages and disadvantages.

Barnes' delay analyst used the as-planned versus as-built windows analysis method, while the Council's delay analyst used a hybrid of the time slice windows analysis and the time impact analysis.

Each witness was questioned and cross-examined on their choice of method used. Barnes' delay analyst was criticised by the other party for not properly following the method chosen, and the Council's delay analyst was criticised for using a combination of methods rather than sticking to a single method throughout.

The judge, in reaching his decision, recognised that there was some weight to the arguments that sought to explain the experts' deviation from the defined analysis methods and stated that it was not appropriate to require a strict adherence to the SCL protocol, noting that the SCL protocol is intended only to provide guidance and not make a statement of the law, nor to form a part of any contract. The judge quoted from the protocol that: "irrespective of which method of delay analysis is deployed, there is an overriding objective of ensuring that the conclusions derived from that analysis are sound from a common sense perspective."

However, the judge did accept that an expert could be criticised on their choice of method, stating that:

"…if an expert selects a method which is manifestly inappropriate for the particular case or deviates materially from the method which he has said he is following, without providing any, or any proper, explanation, that can be a material consideration in deciding how much weight to place on the opinions expressed by the expert."

The case therefore confirms that an expert witness in delay analysis is not obliged to adopt one of a number of certain pre-defined methods and displays that, as with any expert witness, their value is in being able to adapt a body of knowledge from a shifting field to the circumstances at hand.


The case clarifies the view on delay experts' evidence that, while it requires to be justifiable in the circumstances, the court will not take an adverse view simply because the witness does not adhere precisely to a standard form of analysis.

Parties to a construction dispute should not necessarily gravitate towards a particular expert in delay analysis simply because of their tendency to adhere strictly to the standard methods of analysis. While it is undoubtedly crucial that an expert understands and is able to apply the commonly adopted methods, this does not mean that a deviation from the common methods cannot be as appropriate depending on the circumstances. What is ultimately important is: that the expert is able to identify their reasons for adopting any particular method, has the ability to justify this reasoning clearly, and maintains clarity when defending their process.


David Arnott


Simon Andrews

Trainee Solicitor