What must the claimant prove? What is the problem of proof?

Lord Nicholls’ willingness in Gregg to accept the loss of chance argument seems to reflect a clear desire to help a claimant overcome evidentiary difficulties in the medical negligence context. He explained that ‘in cases of medical negligence assessment of a patient’s loss may be hampered, to greater or lesser extent, by one crucial fact being unknown and unknowable: how the particular patient would have responded to proper treatment at the right time’.41 _{That, however, is the}

nature of a counterfactual inquiry, and it is addressed by using the balance of probabilities standard of proof. It is true that the existing disease makes it harder for a court to determine what would have happened to the claimant. In other contexts a claimant could have expected to carry on unharmed unless something unusual occurs, such as a defendant’s negligence; in cases such as these where the claimant was already unwell then he would have expected to suffer harm unless the doctor could cure his illness. The loss of chance argument is therefore a solution to help claimants overcome the evidentiary difficulty, as Lord Nicholls makes plain:

In suitable cases courts are prepared to adapt their process so as to leap an evidentiary gap when overall fairness plainly so requires. Fairchild v Glenhaven Funeral Services Ltd is a recent illustration of this in a different context. In the present context use of statistics for the purposes of evaluating a lost chance makes good sense.42

But although proof of causation is more complicated in these cases than in many straightforward scenarios, it is not afflicted with the same kind of ‘evidentiary gap’ as existed in Fairchild. Proof of causation was impossible in Fairchild. By contrast, in Hotson and in Gregg it was merely difficult. These are not cases where the only available evidence was statistical; there was evidence that could be personalised to the individual claimants. This section will explain the conventional

41 _{Gregg (HL) (n26) [27].} 42 _{Gregg (HL) (n26) [31].}

126

approach to what the claimant should prove, and the standard to which he should prove it, and apply this to the evidence available in the cases to show that it was appropriate to insist on traditional principles.

3.1.1 Damage

As argued in the previous chapters, the role of the causation inquiry in negligence is limited and is defined by the doctrines of damage and breach of duty. It is especially important to define the damage that forms the gist of the action from the outset because the negligence inquiry is concerned to determine whether the defendant’s negligence was a cause of this damage, rather than with determining more generally what would have happened absent the negligence.

This is particularly relevant to the analysis of Gregg because the outcome of the claimant’s treatment was still prospective so, apart from the limited heads of damage noted earlier, he had not suffered the harmful outcome to which the ‘chance’ related. This means that even if the claimant’s pre-tort ‘chance’ of recovery had exceeded fifty percent he would not have had a successful claim on traditional principles unless he could prove that he had suffered actionable damage i.e. the harmful physical outcome. This means that Lord Nicholls was wrong to suggest that ‘[t]he patient could recover damages if his initial prospects of recovery had been more than 50%’.43 _{The causation question is not the open-ended question of ‘what position would the}

claimant be in if the defendant had acted carefully?’, but the focused questions of ‘has the claimant suffered actionable damage and was the defendant’s negligence a cause of that damage?’

3.1.2 Causation

It is preferable to use the NESS test rather than the but-for test to address the causal link because it enables the court to pinpoint more accurately the issues of proof that arise.

43 _{Gregg (HL) (n26) [2].}

127

The advantages of the NESS test for causation are clear in Hotson because the NESS test treats each cause as having equal significance since each was equally necessary for the sufficiency of the set of conditions which resulted in the loss. As explained previously, avascular necrosis occurs when insufficient blood vessels remain intact to keep the epiphysis alive. When the claimant first went to hospital some vessels were damaged but some blood vessels remained intact although distorted. The delay in commencing treatment meant that already ruptured blood vessels continued to bleed into the joint thus increasing pressure in the joint and blocking the intact blood vessels. The delay in diagnosing and treating the injury therefore caused damage to those blood vessels that had remained and sealed the claimant’s fate by turning his injury into an inevitability. When applying the NESS test the ‘sufficient set’ for avascular necrosis is ‘insufficient blood vessels intact to keep the epiphysis alive’. The relevant question is whether the blood vessels damaged due to the delay were necessary for the sufficiency of this set. In other words, when the claimant first went to hospital were there sufficient blood vessels remaining intact for the epiphysis to stay alive?

Lord Bridge was quite clear that this was a problem of individual proof and did not involve any deeper problem that would necessitate resort to statistics. He said ‘[i]n some cases, perhaps particularly medical negligence cases, causation may be so shrouded in mystery that the court can only measure statistical chances. But that was not so here. On the evidence there was a clear conflict as to what had caused the avascular necrosis’.44 _{In other words, if the problem was more}

akin to the evidentiary gap cases where there was a lack of understanding of the causal process and the medical evidence could only furnish statistical assessments of risk then there may be a reason for considering the loss of chance approach. But in this case the causal process was understood, the problem was simply one of proof in the individual case and the claimant had not managed to persuade the judge on the balance of probabilities.

Lord Nicholls sought distinguish the facts of Gregg from those of Hotson because there was:

128

…no significant uncertainty about what would have happened to Stephen Hotson’s leg if treated promptly, once his condition at the time of the negligence has been determined on the usual probability basis... Identifying Mr Gregg’s condition when he first visited Dr Scott did not provide an answer to the crucial question of what would have happened if there had been no negligence. There was considerable medical uncertainty about what the outcome would have been had Mr Gregg received appropriate treatment nine months earlier.45

The line that he draws between the degree and nature of the uncertainty in Hotson and in Gregg is not a clear one. Yet regardless of whether proportional recovery would be an appropriate exceptional solution, the ‘evidentiary gap’ in Gregg is not as deep as Lord Nicholls suggests. He rightly observed that statistical evidence alone is unable to identify the cause in a particular case, and statistical probabilities of over/under fifty percent do not translate directly into proof on the balance of probabilities. But, as the next section will illustrate, statistical evidence can have an important role in convincing a court that a causal link is more probable than not in a particular case where the evidence itself is reliable and where it can be personalised sufficiently to the claimant’s case. Medical understanding of the aetiology of cancer may be incomplete but a range of risk factors are known so the statistical information may be personalised taking into account the characteristics of the individual such as age, general health, spread of the cancer etc. Indeed, Lord Phillips took a more rounded approach to the statistical evidence, examining its reliability and making some, limited, attempt to personalise it. The focus of the next section is on the role that statistical evidence can play in informing the balance of probabilities standard of proof because the courts need to understand this fully before they can identify accurately the problems that are raised by claims such as Hotson and Gregg.

45 _{Gregg (HL) (n26) [38].}

129