In 2021 there were two cases where judges at first instance heard detailed argument on material contribution in the context of clinical negligence, Davies v Frimley Health NHS Foundation Trust  EWHC 169 (HHJ Auerbach) and Thorley v Sandwell & West Birmingham NHS Trust  EWHC 2604 (Soole J).
These two cases drew significantly on three clinical negligence cases where material contribution had been found previously – Bailey v MOD  1 WLR 1052, Williams v Bermuda Hospital Board  AC 888 and John v Central Manchester Health Authority  4 WLR 54.
Firstly, is it necessary to consider material contribution? Clearly not if the ‘but for’ test can be answered favourably for a claimant on the balance of probability. This was the outcome in Davies v Frimley Health NHS Foundation Trust where ‘but for’ the delay in administering antibiotics, the patient would not have died of bacterial meningitis.
Secondly, if the ‘but for’ test cannot be answered favourably, in what circumstances might the test be modified on account of material contribution. Only in limited circumstances, and not those arising in Thorley v Sandwell & West Birmingham NHS Trust where there was delay in prescribing warfarin and the patient sustained a stroke. Material contribution did not apply as a stroke, like cancer, is a single event and not cumulative.
The prerequisites for material contribution in clinical negligence cases can be summarised as follows:-
These propositions are illustrated by the clinical negligence cases where causation failed on the ‘but for’ test but succeeded on material contribution.
In Bailey v MOD  1 WLR 1052 the claimant aspirated vomit causing her to suffer a cardiac arrest which in turn caused brain damage. The question was whether the weakened state at the time of the vomit, that prevented her from aspirating it, had been caused by negligent care and/or by pancreatitis, and if both were they cumulative. The trial judge (Foskett J) was not able to say that, absent the negligent care, the cardiac arrest would not have occurred, but he did consider that both the negligent care and the pancreatitis made a material contribution to the patient’s overall weakened state, which in turn prevented the aspiration (para 60  EWHC 2913). It was held that this was sufficient in law to establish causation.
Upholding the trial judge, on appeal, Waller LJ put it thus (para 43):-
“It seems to me … that Lord Rodger in Fairchild accurately summarises the position when he says in paragraph 129 that in the cumulative cause case such as Wardlaw the ‘but for’ test is modified”
and (para 46):-
“In my view one cannot draw a distinction between medical negligence cases and others. I would summarise the position in relation to cumulative cause cases as follows. If the evidence demonstrates on a balance of probabilities that the injury would have occurred as a result of the non-tortious cause or causes in any event, the claimant will have failed to establish that the tortious cause contributed. Hotson exemplifies such a situation. If the evidence demonstrates that ‘but for’ the contribution of the tortious cause the injury would probably not have occurred, the claimant will (obviously) have discharged the burden. In a case where medical science cannot establish the probability that ‘but for’ an act of negligence the injury would not have happened but can establish that the contribution of the negligent cause was more than negligible, the ‘but for’ test is modified, and the claimant will succeed.”
The causative agents must be cumulative and the severity of the disease increase with exposure, or as arises in the clinical negligence context, with negligent delay in the provision of treatment. John v Central Manchester Health Authority provides an example. Here the claimant suffered a head injury and was taken to hospital and there was delay in undertaking a CT scan that would have precipitated urgent treatment. It was found that the defendant’s negligent delay resulted in a materially significant period of raised intra-cranial pressure which materially contributed to the patient’s brain injury. It was impossible to distinguish between the causative potency of the original accident and the consequent delay in treatment and thus the modified rule to the ‘but for’ test applied.
Similarly, in Williams v Bermuda Hospital Board the claimant attended hospital suffering from acute appendicitis. There was delay in undertaking a CT scan that resulted in the delay of treatment (an operation). The patient would have sustained a ruptured appendix in any event and an infection with an accumulation of pus regardless of any negligent delay. The trial judge, nonetheless, found that there was negligent delay of between (about) 2 hours and 4 hours that led to myocardial ischaemia. The judge found that whilst it was possible that the complications the patient developed during and after surgery might have been avoided had an immediate CT scan been obtained, he was not satisfied that they probably would have been avoided, and the claim failed.
The Bermudan Appeal Court disagreed with the outcome inferring that the delay was a material contribution to the myocardial ischaemia. The Privy Council up-held that decision approving the dicta in Bailey v MOD. In relation to successive events, the Privy Council stated (para 39) “The sequence of events may be highly relevant in considering as a manner of fact whether a later event has made a material contribution to the outcome (as Hotson  AC 750 illustrates), or conversely whether an earlier event has been so overtaken by later events as not to have made a material contribution to the outcome. But those are evidential considerations. As a manner of principle, successive events are capable of each making a material contribution to the subsequent outcome”.
Importantly, contribution to risk will not be sufficient in the context of material contribution in clinical negligence cases (this only applies to industrial disease claims, John v Central Manchester Health Authority para 97).
Whether the condition is cumulative is a matter for medical opinion. Cancer is not cumulative (AB v Ministry of Defence  EWCA Civ 1317); a stroke is not cumulative (Thorley v Sandwell & West Birmingham NHS Trust). Tiredness giving rise to weakness when there are negligent and non-negligent causes can be cumulative (Bailey v MOD); delay causing raised intra-cranial pressure can be cumulative (John v Central Manchester Health Authority), as can delayed treatment causing myocardial ischaemia (Williams v Bermuda Hospital Board).
Impossibility of distinguishing between causative potency is just that: if it is possible albeit difficult, the criteria will not be established. Again, this issue critically relies on medical expert evidence.
The negligent material contribution has to be above de minimis (de minimis being “a transient, trifling, self-limiting, reversible reaction to an irritant” Saunderson & others v Sonae Indistria (UK) Ltd  EWHC 2264 (Jay J) paras 178 to 194).
If material contribution is established, the claimant is able to recover in relation to the entirety of their injury without apportionment (John v Central Manchester Health Authority para 101). This has to follow as it is only if it is impossible to distinguishing between the negligent and the non-negligent that material contribution applies. This may be above a ‘base line’ of what would have occurred anyway; this aspect is likely to be fact-sensitive and in relation to various heads of loss, John v Central Manchester Health Authority paras 106 et seq illustrate the arguments that might be made by the competing parties.
Material contribution is not a panacea, and is limited in its application due to the strict criteria that must be established in a clinical negligence case: at least for now and until a suitable case reaches the Supreme Court, it being a legal issue which is “ripe for authoritative review” (Soole J in Thorley v Sandwell & West Birmingham NHS Trust para 151). However, it can provide a useful arguable basis for establishing causation.
I am grateful to Darryl Allen QC, who acted for the successful claimant in John v Central Manchester Health Authority, for his insights on material contribution in that case and in clinical negligence generally.
John Meredith-Hardy receives instructions in clinical negligence cases that supplement his other areas of practice in personal injury and insurance law.