A recent TCC decision has provided guidance on the bringing of representative defect claims based on sample evidence and expert statistical analysis. This appears to be the first time the TCC has considered the use of statistical evidence to support such claims. The case is likely to be of relevance to parties considering allegations of endemic failings with regard to specific aspects of construction work.
Amey LG Limited v Cumbria County Council Amey was contracted by Cumbria to provide highways maintenance and associated services for a term of 7 years. The relationship between the parties subsequently deteriorated and following the expiration of the contract, Amey commenced proceedings to recover sums deducted by Cumbria from Amey’s final monthly payment application. In response, Cumbria advanced a number of counter-claims, including a claim for the cost of remedial works to repair a proportion of patching and surfacing works carried out by Amey, which Cumbria claimed to be defective. Cumbria advanced this claim on the basis that it had examined a sample number of patching and surfacing works undertaken by Amey, and that its conclusions as to the defective nature of those samples could be extrapolated to the entirety of the works of that nature undertaken by Amey over the contract period. The extrapolation of Cumbria’s claims meant that the financial value of the losses claimed was much greater than those connected specifically to the samples examined by Cumbria. For one claim, the cost of remedial works for the sampled items was approximately £22,000 but would rise to approximately £1.69 million when extrapolated to the rest of the works. The key questions for the court to determine in relation to extrapolation were: 1. Whether Cumbria was entitled to advance its case based on a sample of evidence. 2. Whether the method of sampling used by Cumbria was acceptable to advance its extrapolation case. 3. If the method was acceptable, whether the statistical evidence in relation to the sample set was sufficient to discharge the legal burden of proof in relation to its claim. Decision The court accepted that the substantial quantities of patching and surfacing works carried out by Amey under the contract made it impractical for Cumbria to have inspected every item of work and to have pleaded and proved its case in relation to each allegedly defective item separately. Cumbria was therefore entitled to advance its case on the basis of sampling. It is unclear from the court’s decision whether it would still have been permissible for Amey to rely on sampling if it was not impractical, but simply more expensive or time-consuming, to prove each item of defective work separately.