Gregg v Scott
House of Lords
Citations:  UKHL 2;  2 AC 176;  2 WLR 268;  4 All ER 812;  PIQR P24;  Lloyd’s Rep Med 130.
The claimant developed a lump under one of his arms. A doctor at the defendant’s surgery told him that it was non-cancerous. This was a misdiagnosis: a year later, the claimant discovered he had non-Hodgkin’s lymphoma. The tumour had since spread. Expert evidence indicated that if the claimant had been treated when the lump was first discovered, he would have had a 42% chance of recovery. By the time he received treatment, his chances of survival were 25%.
The claimant sued the defendant in negligence. The defendant argued that the claimant had not established causation. On the balance of probabilities, the claimant could not demonstrate that he would have been better off if treated earlier. He could not establish the ‘but for’ test of factual causation.
- Can a claimant establish causation in circumstances where his chances of recovery but for the breach are under 50%?
The House of Lords held in favour of the defendant. The claimant could not establish factual causation, and no exception applies to this kind of case.
This Case is Authority For…
To establish causation, the claimant must show it is more likely than not that the harm would have been avoided but for the breach. The ‘loss of a chance’ is not an actionable head of damages.
Lord Hoffman stated that there is an exception to this rule where the outcome depends on the unknown decisions of a third-party, such as in Allied Maples Group Ltd v Simmons & Simmons  1 WLR 1602. He argued this was a matter of policy.
Lords Nicholls and Hope dissented. Both agreed that claimants in ‘lost chance’ cases lose something valuable and should get damages. Lord Hope thought that the defendant’s negligence had caused, on the balance of probabilities, the claimant’s tumour to enlarge and spread: this was an actionable form of damage.
Baroness Hale (in the majority) argued that this analysis was flawed. She reasoned that where the defendant did not cause the disease, the claimant cannot establish causation just by showing that the disease got worse during the delay. Rather, the claimant must show (on the balance of probabilities) that his disease would not have gotten worse if he had been promptly treated. The claimant in this case could not do this.
Lord Nicholls described the law as ‘irrational and indefensible’: it makes (for example) a reduction from 51% to 49% actionable, but not a reduction from 49% to 1%. It makes doctors’ duties unenforceable in any case where the patient is already more likely than not to suffer the harm. He noted that claimants have succeeded in negligence in cases where they have lost the opportunity making an economic gain (such as in Allied Maples Group Ltd v Simmons & Simmons  1 WLR 1602). He did not think that the facts of Gregg could properly be distinguished from these cases.
However, Lord Nicholls thought that these principles should only apply where there is uncertainty over the claimant’s prospects. On this basis, he distinguished Hotson v East Berkshire Area Health Authority  AC 750. Lord Hope also distinguished Hotson, arguing that in Gregg ‘at the date of the doctor’s negligence the effect of the delay on the appellant’s prospects of a successful outcome still lay in the future’. He did not think this was the case in Hotson. Lord Hoffman (in the majority) thought the two cases were indistinguishable. Either the two claimants were going to recover, or they were not – ‘the outcome was not random; it was governed by laws of causality’.
Baroness Hale disagreed with Lord Nicholls’ analysis because, taken to the extreme, it would mean that most claimants could not recover full damages. It would transform tort from an area of law which looks at outcomes to one which looks at chances. For example, a claimant who established a 90% chance of avoiding injury would get only 90% of the damages. This approach would make trials far more complex and require expert evidence even in clear cases.