AIMS AND OBJECTIVES
After reading this chapter you should be able to:
■ Understand the usual means of establishing causation in fact, the “but for” test
■ Understand the problems that arise in proving causation in fact where there are multiple causes of the damage
■ Understand the possible effects on the liability of the original defendant of a plea of novus actus interveniens, where the chain of causation has been broken
■ Understand the test for establishing causation in law, reasonable foreseeability of harm, so that the damage is not too remote a consequence of the defendant’s breach of duty
■ Understand the requirements for a plea of res ipsa loquitur, and the effects of a successful plea
■ Critically analyse the concepts of causation in law and causation in fact
■ Apply the tests to factual situations to determine whether the defendant has caused the damage suffered by the claimant
Once the claimant has shown the existence of a duty of care and proved that it has been breached by falling below the appropriate standard of care he must still prove that the defendant’s negligent act or omission actually caused the damage.
As with the other two elements of negligence, the burden is on the claimant to prove the causal link on a balance of probabilities. This may actually be quite difficult to do, particularly where the incident leading to the damage has been the result of multiple causes or where the damage suffered is of an unusual type.
Causation is also clearly appropriate to other torts, not just negligence. Even in those torts that are strict liability and where the claimant as a result is relieved only of the burden of proving fault causation is still an issue and the claimant must still show a direct link between the defendant’s acts or omissions and the damage suffered.
In establishing negligence the courts will measure causation in two different ways:
‘but for’ test
The main test for establishing factual causation in an action for negligence – but for the defendant’s breach of duty the damage would not have occurred
■ according to the “but for” test, that the defendant’s negligent act or omission did in fact cause the claimant’s damage (causation in fact);
■ by establishing that the damage is still sufficiently proximate in law to hold the defendant liable to compensate the victim (causation in law – more commonly referred to as remoteness of damage). (This latter area is the subject of section 4.5.)
The simplest proposition, and the effective starting point in establishing causation, is to say that the defendant will only be liable in negligence if the claimant would not have suffered the damage “but for” the defendant’s negligent act or omission.
The test was explained simply and precisely by Lord Denning in Cork v Kirby MacLean Ltd  2 All ER 402.
In many cases where the negligence of the defendant is obvious the facts allow the test to operate simply and straightforwardly. The negligence either was the cause of the damage or there was some alternative cause and the defendant is not liable.
“if the damage would not have happened but for a particular fault, then that fault is the cause of the damage; if it would have happened just the same, fault or no fault, the fault is not the cause of the damage”.
Barnett v Chelsea & Kensington Hospital Management Committee  1 QB 428
Three night watchmen from a college went to the casualty ward of the hospital at around 5.00 a.m. on the morning of New Year’s Day complaining of vomiting and stomach pains after drinking tea. The doctor on duty, in clear breach of his duty towards the men, then refused to attend to them or examine them and told them to call on their own doctors in the morning. A few hours later one of the men died, as it was discovered later, through arsenic poisoning. The court found that the hospital was not liable for the failure to treat, even though this was a clear breach of their duty, because it was shown that the man would not have recovered even if he had received treatment. The failure to treat was not the cause of death.
However, the facts of a case will not necessarily always be as straightforward as this. In consequence there can be difficulties in establishing causation. For instance, the test may have to be applied to an omission rather than to an act itself, in which case the court has to determine what would have happened if the defendant had chosen to act rather than to do nothing. Only then can the court be sure that the defendant’s omission is in fact the cause of the damage suffered by the claimant.
Brock v Frenchay Healthcare Trust  (Unreported)
Here a 16-year- old boy suffered irreversible brain damage after a fall from a bicycle when he had not been wearing a crash helmet. He had been taken immediately to hospital but the doctors had failed to discover that he had a fractured skull, although it was accepted that there was no negligence involved. The boy was discharged but was readmitted after it became apparent that he was seriously ill. Doctors prepared for an emergency operation and to give the boy a drug, Mannitol, used to relieve pressure on the brain. In the event the anaesthetist did not use the drug until the surgeon arrived and the issue before the court was whether the eventual damage could have been averted if it had been administered earlier. The Court of Appeal, applying the principles in Bolitho v City and Hackney HA  4 All ER 771 (see later in section 4.3.1), held that there was nothing in the evidence to suggest that the drug, if used earlier, would have had any significant impact on the actual injuries.
It is of course possible that the defendant’s injury follows naturally from the negligent omission, because the events leading to the damage would not have occurred but for the negligent omission.
Chester v Afshar  UKHL 41;  4 All ER 587
Here as we have already seen (see Chapter 3.4.3), the Court of Appeal held that the surgeon had fallen below the appropriate standard by failing to give full information on the risks of neurological damage from an operation. The Court accepted that there was evidence to show that the claimant would not have undergone the operation but for the failure to advise of the risks, even though she admitted that she may have been prepared to have the operation at a later stage. It was a simple logic for the Court to accept that the injuries arose directly from the operation, which, even though not carried out negligently, would not have taken place but for the omission to warn of the risks. The House of Lords acknowledged that the problem facing the claimant was that she had admitted that she would have had the operation at some point in the future but not at that time so that it is hard to say that the negligent omission to reveal the full extent of the risks by the doctor could be said to be the direct cause of the injury suffered. Nevertheless, the House, as in Fairchild (see 4.3.1), was prepared to avoid the problems associated with applying the “but for” test in order to give a just result.
Their Lordships appear to be inconsistent in their reasoning. Lord Steyn stated:
“it is a distinctive feature of the present case that but for the surgeon’s negligent failure to warn the claimant of the small risk of serious injury the actual injury would not have occurred when it did and the chance of it occurring on a subsequent occasion was very small. It could therefore be said that the breach by the surgeon resulted in the very injury about which the claimant was entitled to be warned.”
“this argument is about as logical as saying that if one had been told, on entering a casino, that the odds on number 7 coming up at roulette were only 1 in 37, one would have gone away and come back next week or gone to a different casino. The question is whether one would have taken the opportunity to avoid or reduce the risk, not whether one would have changed the scenario in some irrelevant detail.”
Very often the problem is not purely one of fact and the process of establishing cause is not so much scientific enquiry as attributing blame. Inevitably interpretation of the factual evidence may still depend on the value judgements used by the court. For instance a pedestrian runs onto the road into the path of an oncoming vehicle that is travelling over the speed limit for the area and the pedestrian is injured. In purest scientific terms the actual cause of the accident is that both parties were present on the road at the same time. It is possible in the circumstances to feel that the pedestrian has done as much as, if not more than, the motorist in causing his own injuries. Inevitably, however, even allowing for a successful claim of contributory negligence, the motorist would be held to have caused the victim’s injuries, because he is blameworthy by exceeding the speed limit.
Even greater problems may occur where the level of knowledge available to the court makes it impossible to pinpoint the precise cause. This may be particularly appropriate where medicine and medical technology is concerned.
The problem of proving a causal link between the defendant’s negligent act and the damage is always made more difficult where there is the possibility of more than one cause. In such instances the court is forced into the position of trying to determine which of the possibilities is the actual cause of the damage suffered. Very often the court will find that it is impossible to do this with accuracy and the claimant may be left without compensation at all.
Wilsher v Essex Area Health Authority  3 ALL ER 801 CA
Here a baby after being delivered was given excess oxygen as a result of the admitted error of the doctor and the baby then suffered blindness through retrolental fbroplasia. The House of Lords identifed that the excess oxygen was just one of six possible causes of the condition and therefore it could not be said to fall squarely within the risk created by the defendants. The court would not impose liability on the defendant in these circumstances although this seems very unfair.
The difficulty of identifying precise cause means that the case law is often inconsistent. The risk then is that the decision will appear on the surface to be unfair to the claimant. This again is all too common where the chance of recovery may have been lost through negligence in medical treatment or diagnosis.
Hotson v East Berkshire Area Health Authority  1 All ER 210
A young boy suffered a fractured hip when he fell out of a tree. The hospital negligently failed to make a correct early diagnosis so that he later developed avascular necrosis, a deformity of the hip. Expert evidence confirmed that he would have had a 75 per cent chance of the deformity even without the failure to diagnose promptly. On this basis the trial judge, and later the Court of Appeal, awarded him 25 per cent of the damages they would have considered appropriate for the condition for the loss of a chance of recovery. The trial judge commented that the hospital had translated the probability of the disability developing into a certainty by negligence in their failure to diagnose. However, the House of Lords allowed the Health Authority’s appeal and would not consider the slim chance of recovery an issue of causation.
Lord Ackner summed up the issue of causation in the case quite succinctly:
‘the deformed hip … was not caused by the admitted breach by the defendants … but was caused by the separation of the left femoral epiphysis when he fell … I have sought to stress that this case was a relatively simple case concerned with the proof of causation, upon which the plaintiff failed, because he was unable to prove on the balance of probabilities that his deformed hip was caused by the defendant’s breach of duty in delaying over a period of five days a proper diagnosis and treatment.’
However unfair the position of the House of Lords may appear there is nevertheless no disputing its legal logic.
‘The emotive speech and obvious feelings for a “lost chance” plaintiff must not let us colour or obscure the real issue – the existence of an “evidentiary gap”. Proof of causation should not be accepted on anything less than the balance of probabilities, as is common with all civil actions.’
T Hill ‘A lost chance for compensation in the tort of negligence by the House of Lords’  54 MLR 511
The House of Lords has had a more recent opportunity to review the law on ‘loss of a chance’.
Gregg v Scott  uKhl 2;  2 Wlr 268
The claimant was concerned about a lump under his arm but his GP failed to refer him to a hospital for tests, dismissing the lump as harmless fatty tissue. When the claimant saw another GP nine months later, by which time he was in considerable pain, he was referred to hospital for tests and cancer of the lymph glands was diagnosed which it was established had spread considerably during the delay. The claimant argued negligence on the part of the original doctor and it was shown that if his condition had been diagnosed on the first visit and treatment had started at that point he would have had a 42 per cent chance of being alive and disease free in ten years, whereas as a result of the delay in treatment his chances of being alive and disease free after ten years had reduced to 25 per cent. The House of Lords, on a split decision 3:2, was unwilling to depart from the principle in Hotson by awarding the claimant a proportion of what he would have recovered if the doctor’s negligence had in fact caused his premature death. Interestingly the House added that, had the claimant sought damages for the pain and suffering experienced during the delay in treatment these might have been awarded.
Lord Hoffmann, delivering the leading judgment held:
‘Academic writers have suggested that in cases of clinical negligence, the need to prove causation is too restrictive … In the present case it is urged that Mr Gregg has suffered a wrong and ought to have a remedy [and that] the exceptional rule in Fairchild should be generalised and damages awarded in all cases in which the defendant may have caused an injury and has increased the likelihood of the injury … It should be first noted that adopting such a rule would involve abandoning a good deal of authority.’
Lord Nicholls dissenting, on the other hand stated:
‘Given the uncertainty of outcome, the appropriate characterisation of a patient’s loss in this type of case must surely be that it comprises the loss of a chance of a favourable outcome, rather than the loss of the outcome itself. Justice so requires … And this analysis of a patient’s loss accords with the purpose of the legal duty … to promote the patient’s prospects of recovery by exercising due skill and care in diagnosing and treating the patient’s condition. This approach also achieves a basic object of the law of tort. The common law imposes duties and seeks to provide appropriate remedies in the event of a breach of duty. If negligent diagnosis … diminishes a patient’s prospects of recovery, a law which does not recognise this as a wrong calling for redress would be seriously deficient …’
A claim for loss of life expectancy may give rise to compensation.
JD v Mather  EWCH 3063
A claimant with a malignant melanoma was not diagnosed by his doctor for six months after it should have been. In fact his original chances of surviving ten years were under 50 per cent so he could not prove that he might have been cured. However, the tumour had developed into a worse category by the time it was diagnosed and since life expectancy for this category was three years less he was able to claim for three years’ loss of life expectancy.
Ultimately the legal justification for failing to provide a remedy in the ‘loss of a chance’ cases lies in the fact that the claimant’s arguments on causation rests on a possibility rather than a probability of harm occurring, and on a simple balance of probabilities test the claims fail.
The reverse possibility of course is that the court chooses to accept the chance of a causative link between the defendant’s acts and the damage. However, in this instance it may risk the possibility of unfairly penalising the defendant.
McGhee v National Coal Board  3 All ER 1008
Here the claimant worked in a brick kiln where he was exposed to brick dust, a possible cause of the dermatitis that he in fact contracted. The Board was not liable for exposure during working hours. They were held liable for materially increasing the risk of the claimant contracting the disease because of their failure to provide washing facilities, even though it could not be shown that he would have avoided the disease if there had been facilities. The reasoning of the court was that, since the employer was clearly negligent in failing to provide basic health and safety the burden should shift on to them to disprove the causal link. This type of test is clearly more advantageous to a claimant than the basic ‘but for’ test applied so rigidly in Hotson v East Berkshire AHA  1 All ER 210.
The problems that the courts have in determining cause are further added to in circumstances where they are also asked to decide the possible outcomes of hypothetical situations.
Bolitho v City and Hackney Health Authority  4 All ER 771
Here the doctor had been negligent in failing to attend a child with severe respiratory difficulties despite the requests of the nursing staff for her attendance. The doctor claimed that this fact was irrelevant in relation to the cardiac arrest and eventual death of the child. Her argument was that, even if she had attended the child with the breathing difficulties she would not in any case have intubated and thus the same damage would have occurred and that there was responsible medical opinion that would support the practice in the circumstances of the case. The House of Lords rejected the idea that the Bolam test should be applied to the issue of causation in order that the Health Authority should escape liability.
Nevertheless, there are occasions where the courts appear to take a pragmatic approach where proof of causation is difficult.
Bonnington Castings Ltd v Wardlaw  AC 613
The claimant contracted pneumoconiosis after years of working in dusty conditions and without adequate washing facilities. There were two principal causes of dust, the one requiring no extraction system and the other which did, but no extractor was provided. It was impossible to prove accurately which dust the claimant had inhaled most of. Since the dust which should have been extracted legally was at least a partial cause of his illness the court were prepared to award compensation.
The courts are also at times prepared to accept the chance of a causal connection with the damage or the chance of damage being avoided without the defendant’s negligent act or omission.
Stovold v Barlows, The Times, 30 October 1995
It was claimed that a house sale was lost through the negligence of the solicitors. The Court of Appeal felt that there was at least a 50 per cent chance that the deal would otherwise have gone through and so awarded half damages.
But equally courts have been prepared to place too much emphasis on a single cause out of a number of possibilities, leading to unfair treatment of the claimant.
Fairchild v Glenhaven Funeral Services Ltd and others  1 WLR 1052, CA
This case involved a number of appeals. The claimants suffered mesothelioma after exposure to asbestos dust over many years working for a number of different employees. The medical evidence identified that the inhaling of asbestos fibres was the cause of the disease. Nevertheless, it was impossible to identify in which particular employment the disease was actually contracted. The Court of Appeal accepted that medical evidence could not identify a single cause of the disease, which might be caused by contact with even a single asbestos fibre, or may involve cumulative exposure to fibres. As a result the Court held that the precise employer responsible could not be identified and so the claim should be rejected. It is impossible to say with certainty how the disease begins, but it is possible to identify that prolonged exposure worsens the risk. It seems then that the Court of Appeal applied Wilsher v Essex AHA  3 All ER 801 inappropriately where McGhee v NCB  3 All ER 1008 might have been more fairly applied in the circumstances. The House of Lords has in any case subsequently reversed the Court of Appeal decision (see section 4.3.3).
The decision in the Court of Appeal inevitably led to criticism.
‘The “single hit” theory that one asbestos fibre alone is capable of initiating mesothelioma has been the source of incalculable harm … The key point is that the “single hit” theory presupposes a deterministic view which is not supported by science. It encourages a mindset much closer to criminal law – equating the “guilty” fibre with the knife or bullet which severs the victim’s aorta. Of course, lawyers, like most non-scientists, find it hard to resist reducing a complex process to an easily visualised analogy. But they must not forget that the notion of the “guilty” fibre has no basis in the epidemiological evidence … The counter-argument that it is unjust to impose liability upon those not responsible for the “guilty” fibre … overlooks the role of tort in deterring all negligent behaviour not simply that which can be shown to result in actual injury.’
C Miller, ‘Why the House of Lords must overturn the Fairchild decision’ (2002) 152 NLJ 319
Multiple causes can arise generally in one of two ways:
■ the multiple causes are concurrent; or
■ the multiple causes are consecutive.
Inevitably the role of the court is to determine and apportion liability and the result may be different in either case.
If the damage is caused by multiple causes that are acting concurrently, or at the same time, then the ‘but for’ test appears to be incapable of providing an absolute test of causation. The case law demonstrates the difficulties faced by the courts in trying to identify the precise cause.
On the one hand the court may decide that the negligence has ‘materially increased the risk’ of damage and that the defendant should therefore be liable for damages.
McGhee v National Coal Board  3 All ER 1008
Here, as we have already seen, the court was prepared to make the employer liable for the dermatitis suffered by the worker in the brick kiln. The court did so because it considered that the risk of the particular damage occurring had been materially increased by the defendant’s negligent failure to provide adequate washing facilities, even though it was impossible to pinpoint the lack of washing facilities as the precise cause of the condition.
Where the courts use this ‘material contribution test’ it can be difficult in any case to determine the exact extent of the defendant’s contribution and this naturally leads to some strange and apparently arbitrary decisions.
Holtby v Brigham & Cowan (Hull) Ltd  3 All ER 421
Here, the claimant had been exposed to asbestos fibres by a number of employers over a period of more than 40 years. When he contracted asbestosis he sued the defendants, for whom he had only worked for half of that time. The trial judge reduced damages by 25 per cent. The claimant appealed and tried to argue for application of the principle in McGhee, that once having established a material contribution by the defendants he was entitled to full damages. The Court of Appeal rejected his argument and upheld the trial judge’s award, even though 50 per cent deduction would have seemed more accurate. McGhee was distinguished.
In comparison, where there is a number of possible concurrent causes of the damage and it is impossible to identify one specific cause responsible for the damage, then it is unlikely that the court will hold that a single cause is ultimately responsible. The consequence of this of course could be that the claimant is left without an action at all, even though the damage must have resulted from one of the causes. While perhaps technically accurate it also seems potentially unfair.
Wilsher v Essex Area Health Authority  3 All ER 801, CA
Here the court identified that there were at least five other possible causes of the baby’s blindness and the claimant thus could not establish the necessary causal link with the defendant’s negligence and was without a remedy.
Where causes leading to the loss or damage suffered are consecutive, or come one after the other, then ordinarily the liability will remain with the first event unless subsequent events have added to the damage. The ‘but for’ test will be applied to the original defendant.
Performance Cars Ltd v Abraham  1 QB 33
The defendant negligently drove his vehicle so that it collided with a Rolls Royce car. When the Rolls Royce was also later negligently struck by another car the court held that this did not relieve the original defendant of liability for a respray that had in any case been made necessary by the first collision.
In this way where a pre-existing condition of the claimant has contributed to the eventual damage it has been held that this may affect the extent of the liability of the defendant.
Cutler v Vauxhall Motors  1 QB 418
The claimant suffered a grazed ankle following his employer’s negligence. The claimant already suffered a varicose condition and when an ulcer formed on the area of the graze he required an operation. While the defendant was held liable for the negligence the court identified that the liability applied only in respect of the graze, not the operation.
However, a court when it is trying to determine where liability lies in the case of consecutive causes has inevitably at times been influenced by the desire to avoid in any way under-compensating the victim.
Baker v Willoughby  AC 467
The claimant was knocked down by a car and suffered a permanent stiff leg as a result. He was then forced to take work on a reduced income. At a later time he was shot in the injured leg during an armed robbery and this resulted in the leg having to be amputated. The House of Lords rejected the driver’s claim that he was then only liable for damages up to the point of the amputation. The court identified that the loss of earnings was a permanent state of affairs and had resulted from the original injury. The armed robbery and amputation of the leg had not altered this fact even though the eventual damage was different and worse.
Lord Reid explained why in his judgment:
‘A man is not compensated for the physical injury; he is compensated for the loss which he suffers as a result of that injury. His loss is not in having a stiff leg; it is in his inability to lead a full life, his inability to enjoy those amenities which depend on freedom of movement and his inability to earn as much as he used to earn or could have earned if there had been no accident. In this case the second injury did not diminish any of these. So why should it be regarded as having obliterated or superseded them?’
Nevertheless, the picture is even less straightforward because the courts have also at times been keen to ensure that the victim is not over-compensated at the expense of the defendant. Again the principle is that the defendant should only be liable for the extent of the damage actually caused by him.
Jobling v Associated Dairies  AC 794
In 1973, and as a result of his employer’s negligence, the claimant slipped on the floor of a refrigerator in his employer’s butcher’s shop and injured his back losing 50 per cent of his earning capacity as a result. Then in 1976 he later developed spondylotic myelopathy, a crippling back disorder which was in fact unrelated to the fall. The court held that the defendant employer was liable for damages only up to the condition developing in 1976, since the condition, and therefore any further loss of earnings, would have occurred anyway despite the original negligence. The court, while not overruling Baker v Willoughby, was nevertheless very critical of the case.
The two cases taken together demonstrate the important relationship between causation where there are multiple causes and the principles on which damages should be awarded.
■ Where a claimant suffers damage from two separate consecutive causes the second tortfeasor should only be liable for any additional damage caused over that suffered as a result of the first tort.
■ Where a claimant suffers from a condition that is unconnected with a tort that has also caused him to suffer injury or damage of a similar type then the damages imposed on the tortfeasor must be reduced to take into account the effect of the condition.
Interestingly the points that can be taken from the two cases are not necessarily mutually exclusive.
Murrell v Healey  4 All ER 345
The claimant had been injured in two car accidents six months apart, both caused by the negligence of separate defendants. He was paid a settlement in respect of the first claim during which he alleged that it was possible he would be unable to work again. In the second claim, and prior to the actual settlement for the first, he claimed that he did in fact expect to return to work in two months but that the second incident had damaged his knees and hips and that would prevent him from returning to work. This fact was disputed by other evidence in the case of either claim. The trial judge in the second claim held that damages should be reduced by the amount that the settlement from the first covered the same damage. He also held that no post trial loss of earnings should be allowed since the injuries to the knees and hips were not the cause of the second accident. The Court of Appeal held that the judge should have considered any additional damage caused by the second accident. In this way, if the claimant could have done light work after the first accident but that this was prevented by the second then damages should have been based on that. As the claimant had in effect removed this possibility by his evidence in the first claim, no further damages were awarded.
The fact that the courts are prepared to consider the impact that future foreseeable tortious acts may have on termination of the claimant’s employment is yet another source of complication to establishing cause.
Heil v Rankin  2 Wlr 1173
Here a police officer who suffered post-traumatic stress disorder following a car crash was discharged from the police force. The court held that it was a foreseeable consequence of such employment that he would at some point suffer another event that might cause his retirement from the force and that they were entitled to take this into account when assessing damages.
The House of Lords has recently accepted that in certain circumstances where there are a number of defendants all contributing to the same basic injury, then a modified approach to causation has to be taken.
Fairchild v Glenhaven Funeral Services Ltd and others  1 AC 32
This is a major case involving three joined appeals. They all concerned employees who had contracted mesothelioma as a result of prolonged exposure to asbestos dust with a number of different employers. Because of the difficulty of identifying during which employment the disease was actually contracted the Court of Appeal in fact rejected the claims. The House of Lords accepted the expert evidence that it is scientifically uncertain whether inhaling a single fibre or inhalation of many fibres causes the disease, so it is impossible to say accurately which employer caused the disease. However, the House of Lords held that, because it is evident that the greater the exposure to the dust the greater are the chances of the disease occurring, then each employer has a duty to take reasonable care to prevent employees from inhaling the dust. Besides this the House felt that any other cause of developing the diseases could be ignored in the case. On the basis that the claimants suffered the very injuries that the defendants were supposed to guard against, the House of Lords was prepared to impose liability on all employers. The House chose to apply the ‘material risk’ test from McGhee. In doing so the House held that because all of the defendants had contributed to a risk of mesothelioma, then no distinction should be drawn between the making of a material risk of causing the disease and a course of action that would materially increase the risk of the disease. Because the employers in the case never argued that they should only be liable for a proportion of the damages then each employer should be liable to compensate its employee in full, even though the employee may have inhaled more asbestos fibres while working for another employee.
At first sight it is quite difficult to see the precise differences between the three very significant cases of Wilsher, McGhee v National Coal Board, and Fairchild v Glenhaven Funeral Services Ltd and others itself, all of which still stand as leading authorities. A number of points can be made:
■ The judges in the House of Lords in Fairchild accepted that the sufferers of diseases such as mesothelioma, while inevitably deserving of compensation, are unable to satisfy the normal tests for causation because they will invariably be unable to point to a single party who is responsible.
■ because claimants in such actions were unable to satisfy the normal tests for causation only because of the current state of medical knowledge on the disease, although there could be no doubt that exposure to the asbestos fibres in whatever volume was at the root of the disease;
■ as a result of this it was fairer to give the defendants the burden of proving that their negligence could not be the actual cause rather than make the claimants prove the precise cause;
■ and if the House did not take this approach then it would be almost impossible for such claimants to ever make successful claims for the disease in which case the employer’s duty of care would be made meaningless as they could almost never be made liable.
■ The majority of the judges were therefore prepared to accept an exceptional principle that where there was proof that a defendant’s negligence materially increased the risk of a claimant suffering from a particular disease then this would be sufficient basis for a claim against that defendant. This was said to be based on the principle in McGhee.
■ The Court was not prepared to extend the principle in McGhee to factual circumstances such as those in Wilsher where the problem for causation was in fact that there was a number of very different potential causes of the injury other than the defendant’s negligence, and evidence would be needed to show that the negligence was the actual cause.
As Lord Bingham stated:
‘It is one thing to treat an increase in risk as equivalent to the making of a material contribution where a single noxious agent is involved, but quite another where any one of a number of noxious agents may equally probably have caused the damage.’
■ The House of Lords appears to have engaged in a policy decision in order to ensure that there is compensation for asbestos related diseases contracted in the course of employment.