The question of causation in Bailey

The decision of the Court of Appeal in Bailey was notable for showing confusion over the meaning and applicability of the Wardlaw test of material contribution to harm. Waller LJ, with whom Sedley and Smith LJJ concurred, approached the issue by asking ‘was this a case in which the judge was entitled to depart from the but-for test?’129 _{As this chapter has argued, the legal}

issues cannot be fully articulated if the but-for test is taken as the frame of reference, because the but-for test is conceptually inadequate. Using the NESS test makes the resolution of the case simpler and reduces the potential for future confusion.

As noted above, the claimant in Bailey was in a weakened state and therefore aspirated her vomit leading to cardiac arrest and brain damage. The defendant’s negligence had led to weakness, and she was also weakened by a naturally occurring illness. The question was whether the negligent failure to resuscitate the patient after her first operation was a cause of her ultimate injury. The first step is to determine whether the damage is divisible; the damage in Bailey was the brain injury which in this case was indivisible. The cause of the brain damage was the claimant’s

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weakened state which prevented her from responding naturally to her vomit. Applying the NESS test, the question is whether the weakness that was due to the defendant’s negligence was a necessary element of a sufficient set that actually occurred? Since the patient gradually became weakened and this overall weakness led to her failing to respond to her vomit, it is clear that the weakness formed an ‘indecipherable mass’ because the effects operated on her simultaneously. It was the overall weakened state that caused the damage, and the negligence contributed to the total level of weakness, so it was a cause of the claimant’s brain damage. The judge at first instance seems to have understood that this was a relatively simple issue, explaining that although he could not say ‘whether the contribution made by [the negligence] was more or less than that made by the pancreatitis…the natural inference is that each contributed materially to the overall weakness and it was the overall weakness that caused the aspiration’, so he found that the causal link had been established.130

In the Court of Appeal, Waller LJ eventually concluded that causation could be established using the test of material contribution to harm, but his reasoning was more complex since he considered this test to be an exception to the but-for test. He therefore asked whether it was a case in which he was entitled to depart from the but-for test which led him to weigh up the policy arguments and to seek to distinguish the case from a range of other exceptional approaches such as the loss of chance argument and the Fairchild exception. Waller LJ saw the following issue as central:

It is important to be clear precisely what Wardlaw decided. Did it decide that in a cumulative cause case where the inadequacies of medical science meant that the relative potency could not be established all a claimant had to establish was a ‘material’ contribution?...or did a claimant still have to establish that ‘but for’ the contribution of the negligent cause, the injury would not have occurred?131

130 _{Bailey v Ministry of Defences, Portsmouth Hospitals NHS Trust [2007] EWHC 2913 (QB), [61] (Foskett J).} 131 _{Bailey (n119) [39] (Waller LJ)}

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This phrasing of the issue has a number of weaknesses: it assumes that proof of a material contribution does not satisfy the but-for test; it does not address the nature of the damage; and it assumes that the Wardlaw approach was necessitated because it involved cumulative causes and because the relative contributions could not be measured with precision. Waller LJ did not engage with these questions in any depth, but was satisfied that Lord Rodger had established in

Fairchild that ‘in cumulative cause cases such as Wardlaw the but-for test is modified’.132 _As

discussed in this chapter, however, the NESS analysis shows that where damage is divisible ‘material contribution to harm’ translates as applying the but-for test (as shorthand for the NESS test) to a portion of the overall damage, and that where the damage is indivisible it also translates as applying the but-for test where the victim was only exposed to the threshold amount of the harmful agent. It is only where indivisible damage occurred and the causes are duplicative that a test of material contribution would be an exception to the but-for test. But in these cases, if the

Wardlaw test is applied consistently with the NESS test, then it makes up for the conceptual

inadequacy of the but-for test and is not an exception to the factual causation requirement. This means that there is no need to consider, as Waller LJ did, whether a departure from the but-for test is justified on policy grounds. Waller LJ considered arguments that have been raised in the medical negligence context, but that relate to claims based on the loss of chance idea or on the

Fairchild exception, and these arguments are exceptional. In other words, by failing to observe

that the but-for test is conceptually inadequate and needs to be supplemented in order to accurately test factual causation, Waller LJ made life difficult for himself and weighed up policy factors that extend beyond corrective justice and which are unnecessary.