The balance of probabilities

The issue is not just limited to what the plaintiff would have done, but for the breach but, what the defendant would have done in hypothetical circumstances, which have not arisen because of the defendant's own negligence. The courts approach this similarly in that it requires the claimant to prove that but for negligence, the damage would not have occurred. Bolitho v City and Hackney Health Authority [1997] A child suffered brain damage from cardiac arrest. When the doctor was summoned, she had not appeared. This, she admitted was her negligence.

However, she also said that even if she had appeared, she would not have applied 'intubation' which was perhaps the only way the deceased could have been saved. There was evidence that a responsible body of medical opinion would have done the same. In judgment it was held that 'but for' the doctor's negligence, the child would still die. Lord Simon Brown (dissenting) argued that 'in determining matters of causation, the question that should be asked is what would have happened, not whether a responsible body of professional opinion agrees with what the defendant says he would have done'.

In the HoL Lord Wilkinson said '… in all cases the primary question is one of fact: did the wrongful act cause the injury? But in cases where the breach of duty consist of an omission to do an act which ought to have been done the factual enquiry would necessarily be hypothetical. Thus in Bolitho, he raised the following: 1. What would the doctor have done if she attended 2. If she did not intubate is it negligent. The first is a hypothetical factual enquiry. The second may be vindicated with the Bolam test.

Thus, causation is about what in fact happened, which in turn depends upon the hypothetical question what would have happened had here been no negligence ('but for' test). In Bolitho the damage would have occurred even if she attended to the patient (no causation). But one cannot escape liability by proving that she would have failed to act as any reasonable competent doctor would have acted in the circumstance: 'A defendant cannot escape liability by saying that the damage would have occurred any event because he would have committed some other breach of duty thereafter'.

In Joyce v Wandsworth Health Authority [1996] The claimant had after surgery, which was not necessarily negligent developed a condition that she charged was due to poor aftercare. It was given that the only way she could have averted her unfortunate eventuality was if she was seen by a surgeon who would operate on her. Thus, she had to prove that if proper care had been given she would have been referred to a surgeon who would operate on her. If she could do so, she would have established that 'but for' the defendant's negligence she would not have suffered. She did.

The plaintiff succeeded in action against the defendants as he could prove that his condition would not have worsened 'but for' the doctor's negligence. Capital and Counties plc v Hampshire County Council [1997] The fire brigade had arrived at the scene of a fire and bizarrely switched off the sprinkler system. The building was completely destroyed. The fire brigade argued that even if the sprinkler system was not switched off, the defendants cannot prove that the damage would have been averted. The Appeal Court held that the defendants by their positive act exacerbated the fire so that it spread.

They compared the eventuality with the hypothetical notion of not switching off the sprinklers and found for the claimants. Although the fire service is not obliged to prevent damage by fire, they cannot exacerbate it. Another approach to factual causation is to ask whether the damage was within the risk envisaged by the defendant's fault. In Gorris v Scott (1874), it was held that although the loss (of the claimant's sheep) would not have occurred but for the breech of the statutory duty to keep animals in pens so as to minimize disease risk, it was not caused by the breach which envisaged an entirely different risk.

In Darby v National Trust [2001], it was held that the risk of contracting Weil's disease and drowning were fundamentally different and as such the alleged duty to take reasonable care to warn against the risk of contracting that disease could not form the basis of a claim for damages attributable to a different cause. Similarly, in the case of The Empire Jamaica [1957], it was held that not having the physical certificate of exemption was not the causation of the collision of the ship when the mate who was duly qualified to handle it but failed to apply for exemptions.

Thus, 'but for' the mate not having the relevant certificates physically, the collision would have still occurred. In Barker v Willoughby [1970] it was held that where the defendant's tort results in the claimant having to change his job, the tort is not per se a 'cause' of subsequent damage sustained by the claimant in the course of his new employment. Here, factual causation shades into causation of law. Proof of Causation It is important to prove, on the balance of probabilities, that the defendant's breach of duty caused the damage.

The onus of providing such evidence generally lies with the plaintiffs, although the defendant may produce rebutting evidence. Pick ford v Imperial Chemical Industries plc [1998] This is an example for the need to provide robust rebuttal where facts of the case are contentious. However, the defendant's failure to proof that his version is the correct one where there are contentious conflicting facts may be a factor in deciding whether the claimant's explanation of the causes should be accepted. Reay v British Nuclear Fuels plc [1994]

This is authority for a need to for the plaintiffs to proof that on the balance of probabilities, the negligence of the defendants caused the injury. In this case, the plaintiffs failed to establish, on the balance of probability, given the many sources of contracting the condition, that paternal pre-conception irradiation causing sperm mutation and hence predisposition to cancer in children. In Kay v Ayrshire and Arran Health Board [1987] the plaintiffs failed to proof that penicillin overdose could cause deafness.

In Loveday v Renton [1990] plaintiffs failed to show on the balance of probabilities that the pertussis vaccine causes brain damage in young children although it was possible that it did. Hotson v East Berkshire Area Health Authority [1987] This is authority for cases where on the balance of probability, the damage would have occurred and thus the 'but for' causation unsatisfied. The claimant had sustained a fall that led to hip injury. The claimant was sent to hospital and was negligently treated.

Subsequently his condition worsened. However, he could not, on the balance of probability, prove 'but for' the negligence of the hospital, he would not have suffered as evidence showed that he had only a 25% chance of recovery. Applying Diplock LJ view on probability (Anything that is more than not is treated as certain), the claimant lost. Generally, anything more than probable is treated as a certainty (and vice versa) (Mallett v McMonagle [1970]). Bonnington Castings Ltd v Wardlaw [1956]

This is authority for material contribution where claimant cannot establish 'but for' causation due to inability to quantify contribution to damage between possible causes. The HoL held that a claimant does not have to establish that the defendant's breach of duty was the substantial cause of damage as long as they can prove, on the balance of probability that it materially contributed the disease. The claimant contracted lung disease from inhaling dust-polluted air in his workplace.

There were generally 2 kinds of dust – 'innocent dust' where there was no breach of duty on the part of the employers and 'guilty dust' where the employers had failed to maintain requisite dust extraction machinery, from different sources within the workplace. On evidence, there was no proportion of dust inhaled by the plaintiff and thus could not establish 'but for' causation, in the sense that it was more probable than not that had dust extraction machine worked efficiently he would not have contracted the disease.

Nonetheless, the HoL drew inference of the fact that the 'guilty dust' was a contributory cause, holding the employers liable for the full extent of the loss. The plaintiff did not have to proof that the guilty dust was the sole or even the most substantial cause as he could show on a balance of probabilities (the burden of proof remaining with the plaintiffs), that guilty dust had materially contributed to the disease. Anything which does not fall within the principle of de minimis non curat lex would constitute a material contribution.

Subsequently, in Nicholson v Atlas Steel Foundry & Engineering Co. Ltd [1957], on virtually identical facts the HoL held the employers liable even though, in the words of Viscount Simonds, it was 'impossible even approximately to quantify' the respective contribution of guilty and innocent dust. These cases are significant in easing the claimant's burden of proof for 2 reasons: 1. They represent a departure from 'but for' causation – the claimant does not have to prove that he would not have suffered the damage but for the breach of duty.

What he has to be proved is redefined as 'material contribution' to the injury or illness. But notwithstanding that the courts redefine the 'damage' to which the claimant must establish a causal link in more limited terms than the outcome, the claimant still recovers damages for the whole loss. 2. The courts are willing to draw an inference of facts that there had been a material contribution when it was in reality impossible to say whether there had been any such contribution. McGhee v National Coal Board [1972] The claimant contracted dermatitis from the brick kiln he worked in.

Although the defendants were held not liable for the exposure to the dust, they were held liable for not providing washing facility because this increased the period of time during which the claimant was exposed to the dust while he cycled home. While it was agreed that the dust had caused dermatitis, they could not say whether it was probable that the claimant would not have contracted dermatitis if he had been able to take a shower after work. Thus, he could not establish 'but for' causation in respect of 'guilty' exposure'.

At best, it could be said that failure to provide washing facilities materially increased the risk of the plaintiff contracting dermatitis. And it was practice in the industry to provide showers. The HoL held the defendants liable on the basis that it was sufficient for the plaintiff to show that the defendants' breach of duty made the risk of injury more probable even though it was uncertain whether it was the actual cause. The majority of their Lordships treated a 'material increase in the risk' as equivalent to a 'material contribution to the damage'.

Lord Simon said 'the failure to take a step which would bring about a material reduction of risks involves, in this type of case, a substantial contribution to the injury'. This outcome may also be attributed to policy reasons as per Lord Wilberforce. It is to be noted that inference to time of exposure could have been made; nevertheless, the HoL took a less probabilistic stance and this case is important in that the defendants were not under statutory duty to provide showers. In McGhee, Nicholson and Bonnington, the 'material contribution' aspect is succinctly stated:

'If it is established fact that conduct of a particular kind creates a risk that injury will be caused to another or increases an existing risk that injury will ensue, and if the 2 parties stand in such a relationship that one party owes a duty not to conduct himself in that way, and if the other party does suffer injury of the kind to which the risk related, then the first party is taken to have caused the injury by his breach of duty, even though, the existence and extent of the contribution made by the breach cannot be ascertained. ' Wilsher v Essex Area Health Authority [1986]

This is authority for proof of causation where there are multiple potential causes to an eventuality, all having equal chance of being the cause but only one of them is the cause. There were five possible causes including one which was created by the defendant's mistake that could have caused the eventual harm. And the claimant suffered from the harm but he could not, on he balance of probability, prove that 'but for' the defendant's negligence, he would not be blind because there was a 4 out of 5 equal chances that he would be blind anyway.

In the Appeal courts, applying McGhee According to Mustil (in the court of appeal): 'what the defendants did was not to enhance the risk… but add to the list of factor which might do so'. Wilkinson took the position that: 'this case is wholly different from McGhee. A failure to take preventive measures against one out of five possible causes are no evidence as to which of those five caused the injury'. Thus, the claimant failed. Fairchild v Glenhaven Funeral Services Ltd [2002] (UKHL)

This is authority where claimant suffers a detriment (not cumulative) due to the breach of duty by the defendant but claimant, for good reason, could not identify which defendant it was. C was employed by A & B. During his course of employment he caught a disease but does not know from A or B (due to lack of scientific development). Furthermore, the disease is not the 'cumulative type' and the nature of the disease is such that it is sparked off at a single point in time.

Thus, if he caught the disease when with A then that would absolve B and vice versa. All defendants were indeed in breech of duty for not taking steps to limit the possibility of conditions leading up to the disease but it was only that the claimants could not identify whom. The HoL held on the basis that in the special circumstances (and in no other circumstances) of this type, there should be a relaxation of the normal rule that the claimant must prove that 'but for' the defendant's breach of duty, he would not have suffered the damage.

Bingham LJ: '… there is strong policy argument in favor of compensating those who have suffered grave harm at the expense of the employers who owed them a duty to protect them against that very harm and failed to do so, when the harm can only be caused by the breach of the duty and when science does not permit the victim to attribute between several employers…

Such injustice as may be involved in imposing liability on the duty breaking employer in these circumstances is heavily outweighed by injustice of denying redress to the victims'. Fairchild applies where there are multiple defendants in breach of a similar duty because it is unfair or unjust as a matter of policy to deprive claimant compensation because he is unable to prove the impossible.