Another problem arising out of the uncertainty surrounding the reasons for the application of the Wardlaw test is that it has led to uncertainty whether ‘apportionment’ of damages is
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appropriate. If the courts apply the test of material contribution because of a lack of evidence as to the precise proportions of the harmful agent attributable to each source then, it has been argued, it would be inappropriate for the court to apportion liability because it would lack a rational basis on which to calculate the portion of the damage that is attributable to the defendant’s negligence. As already discussed, damages should be ‘apportioned’ where the injury is divisible. Since each source of the harmful agent causes a portion of the total loss, this is a false apportionment – it is not an apportionment of liability but a question of quantifying that portion of the loss attributable to the defendant’s negligence. It is therefore the definition of the damage, rather than the NESS test, that determines the ‘apportionment’ issue. The NESS test, however, is still valuable because it highlights that the Wardlaw test is needed to respond to a conceptual weakness in the but-for test and not because of an evidential problem.
In Hatton v Sutherland,133 a case involving psychiatric illness resulting from occupational stress, the
claimant established causation by showing that the defendant’s negligence made a material contribution to her illness and in the Court of Appeal Hale LJ concluded that where there were multiple causes of a psychiatric injury then apportionment should be attempted. In the decision of the Court of Appeal in Dickins v O2 plc,134 however, it was suggested that where the test of
‘material contribution to harm’ is applied it would be inappropriate to apportion liability regardless of whether the harm was divisible or indivisible. The reason for this conclusion was the court’s understanding that the ‘material contribution to harm’ test is used where the various contributions made by the defendant(s) cannot be quantified.
[I]n a case which has had to be decided on the basis that the tort has made a material contribution to harm but it is not scientifically possible to say how much that contribution is (apart from the assessment that it was more than de minimis) and where
133 [2002] EWCA Civ 76, [2002] 2 All ER 1. 134 [2008] EWCA Civ 1144, [2009] IRLR 58.
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the injury to which it has lead is indivisible, it will be inappropriate simply to apportion the damages across the board.135
Since the extent of the contribution cannot be quantified, the court reasoned that any apportionment would necessarily be artificial:
That means that a claimant can succeed on causation even though he cannot demonstrate what the causative potency of the tort was, save to say that it had some effect beyond the minimal. It seems to me that, if in one breath the judge holds that all that can be said about the effect of the tort is that it made an unspecified material contribution, it is illogical for him, in the next breath, to attempt to assess the percentage effect of the tort as a basis for apportionment of the whole of the damages.136
It is not at all clear that the reason for applying the Wardlaw test is that the relative contributions cannot be quantified. As this chapter has illustrated, the Wardlaw test may also represent an application of the but-for test to a portion of the total loss in cases of divisible damage, and may make up for the conceptual inadequacies of the but-for test in over-determined cases of indivisible damage. Since the nature of the problem addressed by the Wardlaw test is unclear it is natural that there will be confusion in its application. As this chapter has shown, the first step in any case is to define the damage as being divisible or indivisible. Once this has been done, the NESS test can be applied to either type of damage and can resolve problems of pre-emption and duplication. If the damage is indivisible then the negligence is a cause of the whole of the loss so there is no apportionment vis-à-vis the claimant, and joint and several liability applies. If the damage is divisible and the negligence has caused only a portion of the total loss then apportionment is required in principle because the defendant is only causally responsible for a portion of the loss so only that portion of the loss is ‘wrongful’ in corrective justice. If there is an insurmountable evidential barrier to the apportionment exercise then this must be addressed squarely.
135 ibid [46] (Smith LJ).
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Chapter One showed that causation has a vital but limited role in interpersonal responsibility and this chapter has drawn this issue out in greater detail to isolate factual causation, the fact of being
a cause, from evaluative conclusions that a condition was the responsible cause. It was shown
that the NESS test is preferable to the but-for test as a test of factual causation because it is better matched to the philosophical account of what it means to be a cause and is therefore able to resolve more complex causal problems that the but-for test is unable to resolve. Adopting the NESS test would ensure that courts are equipped to address a wider range of causal scenarios without resorting to exceptional tests. This is important because it has shown that cases such as
Wardlaw and Bailey may involve an exception to the but-for test but they do not involve an
exception to the causation requirement. Having addressed the conceptual aspects of causation in this chapter the remaining chapters turn to evidential problems that have arisen and consider how they can be resolved consistently with principles of corrective justice. The work in this chapter will be valuable because the NESS analysis means that the evidential problems can be more clearly identified. The final chapters will also be strengthened by being able to draw on the analysis of the role that causation has within interpersonal responsibility and of the roles of the other negligence doctrines in addressing the remaining aspects of interpersonal responsibility.
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Chapter Three: Loss of a chance
Introduction
The loss of a chance argument has been raised by claimants who have been unable to prove on the balance of probabilities that the defendant’s negligence was a cause of their physical damage. The claims in Hotson v East Berkshire Health Authority,1 and Gregg v Scott,2 arose in the medical
negligence context and in both cases the negligence consisted of the doctor’s failure to diagnose and treat an existing illness. In both cases the court found that on the balance of probabilities the patient’s existing illness could not have been cured with careful treatment, so the delay was not a cause of any eventual physical damage. The claimants argued instead that although it was less than probable that their condition could have been cured, the ‘chance’ of a cure had been reduced by the negligence and this ‘chance’ was something of value. They therefore sought to reformulate the actionable damage as the ‘chance’ of avoiding physical injury rather than the physical harm itself. If it succeeded, this action for loss of a chance would lead to proportionate recovery of damages for the physical harm, for example in Hotson the loss of a 25 percent chance of avoiding avascular necrosis was valued at 25 percent of the total loss caused by the avascular necrosis. Although this argument therefore centres on the question of whether a ‘chance’ of a better outcome can constitute actionable damage in negligence, it is an attempt to sidestep the difficulties of proof of causation of the physical harm on the balance of probabilities standard of proof.
It will be argued in this chapter that the House of Lords was right to reject the claim for proportionate recovery for the loss of a chance of a better medical outcome in both of these cases. In corrective justice-based interpersonal responsibility, liability is for ‘wrongful loss’ and the loss can only be characterised as wrongful if it was, in fact, caused by the defendant’s
1 Hotson v Fitzgerald and others [1985] 1 WLR 1036 (QBD); Hotson v East Berkshire Health Authority [1987] 2 WLR 287
(CA); Hotson v East Berkshire Health Authority [1987] AC 750 (HL).
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negligence. Causation is a factual relationship, so the negligence either was or was not a cause of the harm. The claimant need only persuade the court of this fact on the balance of probabilities and if the court is, on balance, persuaded that the negligence was a cause of the damage then it accepts the fact of causation to be proved and the claimant recovers in full. Although the loss of chance argument ostensibly reformulates the damage as the chance of avoiding physical harm, it will be argued that what it in fact achieves is to ‘discount’ liability to reflect the degree of doubt over the fact of causation.
However, it will also be argued in section 4.2 that the doctor/patient relationship raises unique issues of interpersonal responsibility because the patient’s ‘chance’ is valued by both parties and has intrinsic value independently of the physical outcome. At the time of diagnosis and treatment, the outcome of treatment is uncertain and beyond the control of the parties – the doctor and patient both regard him as having a ‘chance’ in these circumstances and they do what they can to improve his chance – the doctor gives him careful treatment, indeed the purpose of his duty of care when a patient is already ill is to take an uncertain situation and do what he can but he cannot guarantee cure. Both parties therefore take the statistical medical assessment of the likelihood of cure as being something that is valuable to the claimant so a reduction in the statistical chance of cure is a loss of something of value and ought to be recognised as actionable damage. Importantly it is valued for its own intrinsic worth rather than as a proportion of the physical harm. While the practical effect is that loss of chance would ‘assist’ claimants by providing compensation even where the doctor’s negligence is not proved to have caused physical harm, this compensation would be very modest and is certainly not a way to bypass the causation requirement regarding the physical harm.