The Supreme Court has given a rare judgment on the court’s approach to awarding damages for a “loss of a chance” in a professional negligence claim: Perry v Raleys Solicitors [2019] UKSC 5. The decision confirms the approach laid down by the Court of Appeal in Allied Maples Group Ltd v Simmons & Simmons (a firm) [1995] 1 WLR 1602, describing it as establishing a “clear and common-sense dividing line” between the matters the claimant must prove, and those which may better be assessed on a loss of chance basis. In summary:

  • To the extent that the question of whether the claimant has suffered a loss depends on what the claimant would have done in the absence of negligence, that must be proved on the balance of probabilities.
  • To the extent that the supposed beneficial outcome depends on what others would have done, that will be evaluated on a loss of chance basis, applying the relevant percentage to the prospective benefit.

The decision also clarifies the extent of the general rule that, for the purpose of evaluating the loss of a chance, the court does not undertake a “trial within a trial”. The court rejected the notion that it is always inappropriate for the court to try an issue relevant to causation merely because that same issue would have fallen for determination in the trial of the underlying claim which was lost due to the solicitors’ negligence.

The question whether any given issue should or should not be tried in the negligence proceedings depends upon whether it is one upon which the client must prove his case on the balance of probabilities, or only one which should be subjected to the valuation of a lost chance. If the latter, it is generally inappropriate to conduct a trial within a trial. If the former, however, the court said there is no reason why either party to the negligence proceedings should be deprived of the full benefit of an adversarial trial of that issue.

For more information, please see our Insurance and reinsurance disputes ebulletin on the decision.