Definition
Loss of chance in tort law refers to a claim for damages arising where a defendant's negligent conduct has deprived the claimant of a valuable opportunity or prospect, even though it cannot be proven on the balance of probabilities that the opportunity would have materialised. This doctrine allows recovery for the loss of the chance itself, valued proportionately according to the likelihood it would have succeeded, rather than requiring proof that the desired outcome would more likely than not have occurred.
Deep Dive
Historical Development and Recognition
The loss of chance doctrine emerged from the landmark case of Chaplin v Hicks [1911] 2 KB 786, where the Court of Appeal permitted recovery for the loss of opportunity to compete in a beauty contest. The claimant could not prove she would have won, but the court recognised that the chance itself had quantifiable value. This principle established that the law could compensate for lost opportunities where the prospect had real and substantial value, even if uncertain.
The doctrine developed significantly in commercial contexts before courts grappled with its application in professional negligence cases. The critical question became whether loss of chance should extend beyond contractual relationships into pure tort claims, particularly in medical negligence.
Distinction Between Medical and Non-Medical Cases
A fundamental division exists in English law regarding loss of chance claims:
Medical negligence cases:
- Generally require proof on the balance of probabilities (more than 50% likelihood) that the negligent treatment caused the physical injury
- Hotson v East Berkshire Health Authority [1987] AC 750 established that claimants must prove causation on the conventional balance of probabilities test, with the House of Lords confirming that a loss of chance to avoid injury is not compensable in negligence
- Gregg v Scott [2005] UKHL 2 confirmed (by a 3:2 majority) that loss of chance claims for physical injury caused by medical negligence are not recoverable
- If the chance of a better outcome was less than 50%, the claim fails entirely under the "all or nothing" approach
Non-medical professional negligence cases:
- Courts permit recovery for loss of chance where the negligence deprives the claimant of an opportunity to achieve a beneficial outcome
- Allied Maples Group Ltd v Simmons & Simmons [1995] 1 WLR 1602 established the framework for loss of chance claims in commercial contexts, recognising that loss of chance is recoverable in cases of negligent professional advice where the possibility of loss depends on the response of a third party
- Solicitors' negligence cases commonly involve loss of chance analysis, such as lost opportunities to pursue litigation or complete transactions
- Perry v Raleys Solicitors [2019] UKSC 5 affirmed the Allied Maples framework, confirming that loss of chance can be recoverable in cases of negligent professional advice where the chance of a beneficial outcome depends on what others would have done
The Allied Maples Framework
Allied Maples Group Ltd v Simmons & Simmons [1995] 1 WLR 1602 established a critical three-stage test for causation in professional negligence:
- Stage 1: What the defendant would have done but for the negligence – this must be proved on the balance of probabilities
- Stage 2: What the claimant would have done but for the negligence – this must be proved on the balance of probabilities
- Stage 3: What third parties would have done – this is assessed as a loss of chance, valued proportionately
This framework allows courts to award damages reflecting the percentage chance that the opportunity would have succeeded, rather than applying an all-or-nothing approach. As clarified in Perry v Raleys Solicitors [2019] UKSC 5, to the extent that the supposed beneficial outcome depends upon what others would have done, this depends upon a loss of chance evaluation, while matters within the client's own control must be proved on the balance of probabilities.
Rationale for the Medical/Non-Medical Distinction
The House of Lords in Gregg v Scott articulated several justifications for treating medical negligence differently:
- Physical injury cases involve binary outcomes (harm occurred or did not), making percentage-based recovery conceptually problematic
- Opening the floodgates to claims where patients had less than 50% survival prospects could fundamentally alter medical negligence litigation
- Uncertainty about how to measure and value chances of physical recovery
- Policy concerns about defensive medicine and insurance implications
- As Baroness Hale noted in Gregg v Scott, recovery for loss of chance could potentially lead to proportionate recovery across all cases, meaning claimants who currently obtain full recovery would only obtain proportionate recovery, with expert evidence becoming more complex and trials more difficult
Critics argue this distinction is unprincipled, as it treats claimants with 49% prospects worse than those with 51% prospects, despite the negligence being equally culpable. Lord Nicholls in his dissenting judgment in Gregg v Scott argued that loss of a 45% chance of recovery is just as much a real loss as loss of a 55% chance of recovery, and that such an approach accords with the purpose of the duty of care which is to promote the patient's prospects of recovery.
Quantification and Assessment
When loss of chance claims succeed, damages are calculated proportionately:
- The court assesses the percentage probability the chance would have materialised
- This percentage is applied to the full value of the lost opportunity
- In Allied Maples, the lost chance of negotiating a warranty was valued at 50%, so damages were halved
- Expert evidence typically addresses the likelihood of success
The assessment requires careful analysis of hypothetical scenarios and counter-factual questions about what would have occurred absent the negligence. As Lord Briggs explained in Perry v Raleys Solicitors [2019] UKSC 5, there are important policy justifications for the loss of chance approach: where what is lost is a negligence claim with substantial chance of success, it would be absurd to decide the claim on an all or nothing basis, giving nothing if the loss of chance is 49%, particularly since most claims with evenly balanced prospects are settled rather than pursued to trial.
Current Debates and Developments
The loss of chance doctrine remains controversial and continues to generate academic and judicial debate:
- Whether the medical/non-medical distinction can be justified on principled grounds
- The potential for expanding loss of chance into other tort contexts
- How to reconcile loss of chance with fundamental causation principles requiring proof on the balance of probabilities
- Whether reform is needed to create a more coherent approach across all negligence claims
- Lord Hoffmann in Gregg v Scott acknowledged that confining loss of chance to cases where an inability to prove causation results from medical uncertainty rather than evidential uncertainty can lead to unfairness, as it can be equally difficult to prove causation in both scenarios
The minority judgments in Gregg v Scott provide compelling arguments for extending loss of chance to medical cases, suggesting the debate may not be finally settled. Lord Nicholls' dissenting view distinguished medical cases into two categories: cases where there is little uncertainty on the outcome (like Hotson), where loss of chance should be non-recoverable, and cases where the patient's condition gives rise to significant uncertainty, where loss of chance could be actionable damage.