Modification of causation principles
“At the very least Fairchild shows that where justice and policy demand it a modification of causation principles is not beyond the wit of a modern court."
per Lord Steyn in Chester v Afshar  UKHL 41, 
Describe how the courts currently deal with the issue of causation within the law of negligence. How do the judiciary use policy considerations as a means of avoiding adherence to the rules of causation?
Causation is the third element of a claim in negligence. Once the duty of care and breach has been established the next hurdle to over come by the claimant is to establish causation which provides a link or nexus between the defendant’s breach and the claimant’s damage. Causation has two parts:
1. Factual causation
2. Legal Causation
Factual causation and But for Test-
Factual causation deals with establishing the actual physical link between the negligence and damage. Stapleton stated the factual causation as a historical link between the defendant’s negligence and the claimant’s injury. 
The basic test that the court uses to establish factual causation is but for test. But for the defendant’s breach would the plaintiff have suffered the damage. If the answer is yes then the defendant is liable and if the answer is no then some other facts are liable apart from the defendant. The main purpose of this test is to exclude things that have no bearing on the damage. Lord Denning introduced this term in law for the first time in Cork v Kerby Maclean Ltd.  and the test was first established in a classic case namely Barnett v Chelsea Kensington Hospital  where the court found that the but for test had not been satisfied as the evidence showed that the patient would have died any way of arsenic poisoning
In another recent case namely Bolitho v City and Hackney health Authority  the court did not find any causation between the claimant’s damage and the defendant’s breach on the basis of but for test. There was a question to decide before the court .but for the defendant’s breach, would the patient have suffered brain damage any way? The court asked for expert opinion who later opined that most of the doctors would have done the same thing if they were in defendant’s place which meant that the patient would have suffered brain damage any way. But some time the court appeared to depart from the ordinary principle of but for test to secure justice to the plaintiff as can be observed in Chester v Afshar.  In this case although the claimant failed to establish the ordinary but for test, the court departing from the ordinary rule made the defendant liable for the breach of duty owed to the claimant and the defendant was held in breach of duty by not warning the claimant about the side effect of surgery.
Problem with but for Test:
The but for test is found unworkable to deal with the situations where there is more than one cause as it does not allow a full consideration of the different possible outcomes.
Illustration: A develops lung cancer ,and is able to prove that he was exposed by his employer to a chemical that has been proved to cause that type of cancer .however the employers can also point out that for the last 20 years A has been a heavy smoker which could also be the cause of the cancer. But for test does not work in this type of multiple cause situations as any one of the two causes is enough to develop lung cancer.
Multiple Causes classified by the court:
To mitigate this type of multiple cause situations the court has classified multiple causes into three distinct forms.
1. Multiple potential causes: there is more than one cause of the damage and it is not certain which one actually caused the damage. It can be more problematic if those potential causes have been developed over a long period rather than on a single occasion.
Long term multiple causes can be following three types:
A. the claimant may have exposed to damage by the defendants in a range of different situations and some of which were justifiable on the part of the defendant and some were not.
B. the claimant may have exposed to the same cause of injury by different defendants at different times but the effect may be one-off in nature.
C. the claimant may have exposed to the same cause of injury at different times but the exposure may have had cumulative effect.
2. Concurrent causes: there may be two actions or omissions occur at the same time and each action or omission has the potentiality to cause the damage. An example of this is Fitzgerald v Lane and Patel  where the plaintiff was hit by two cars at the time of crossing the road and the medical experts could not state whether the injuries were caused by the action of one or other driver or a combination of both There is another example of concurrent causes namely Bonington castings v Wardlaws  where the cause of the claimant’s disease was exposure to dust at work.the defendants accepted the liability for excessive exposure of dust.
Concurrent causes also cover a situation like Fairchild v Glenhaven funeral Services ltd and others  .in this case the claimant had been exposed to asbestos dust during his employment with a number of employers at different times in the year 1960.The medical experts were unable to say which exposure with which employer was the cause of his illness.
3. Consecutive causes: several causes operate one after another each of which plays role to identifiable damage. Performance Cars v Abraham  is a good example. Here the court of appeal determined that there was no effective damage arising from the second collision as the requirement for a re spray already existed before the collision. But in Baker v Willoughby  the House of Lords surprisingly held that the defendant’s liability would be continuing after the second occurrence in which the defendant got his leg amputed it was thought that the House of Lords decision was just to ensure the justice to the plaintiff.
About the House of Lords decision in Baker v Willoughby Lord Keith and Russel indicated that the second event in Baker was also a tort.  That means if the second event was natural then the House of Lords decision would be different as can be observed from the decision of Jobling v Associated Dairies  in which the court held that the defendant’s liability ceased at the point that the further back injury developed.
Different test introduced by the court to deal with multiple causes:
To deal with the above three forms of multiple causes it is up to the court to decide which test to use depending on the situation of each case. Multiple causes come out with following three tests:
1. Material contribution test or McGhee test: if the plaintiff can prove that defendant’s negligence materially contributed to the risk of damage then the claim will be successful.
This is also known as McGhee test as it was established in McGhee v National Coal Board  .where the court decided that failing to provide washing facilities after work the defendant materially contributed to the risk of dermatitis.
2. Apportionment: if the court is satisfied that there is more than one defendant liable for the plaintiff’s damage then the court apportions the liability. This was what happened in Fitzgerald v lane and patel  .here the court apportioned the defendant’s liability for their breach. The court of appeal held in Fairchild v Glen haven funeral Service  that the plaintiff had to sue each defendant for their contribution to the damage .But the House of Lords decided that plaintiff can sue one of the defendants for the full compensation .Then that defendant can sue others for their portion. Later in Barker v Corus UK Ltd.  The House of Lords overturned their decision and agreed with the Court of Appeal’s decision in Fairchild .To mitigate this turmoil situation the parliament came forward and enacted the provision relating to mesothelioma under section 3 of The Compensation Act 2006 which manifested the House of Lords decision in Fairchild.
3. Balance of probability test: the plaintiff has to prove that the defendant is 51 percent liable for the damage. In Hotson v East Berkshire health Authority  the plaintiff’s claim was failed because the expert opined that there was only 25 percent chance that the misdiagnosis had caused the disability .75 percent was natural.
In Wilsher v Essex AHA  the plaintiff’s claim was also failed because it was not proved that the defendant was on the balance of probability liable for damage. similarly in Gregg v Scott  the House of Lords rejected the plaintiff’s claim of loss of chance stating that the claimant needed to show that the doctor’s negligence made it more likely than no that he could be cured. In this case when the claimant first visited the doctor he was 58 percent likely to die from cancer rather than survive.
In the case of economic loss it was held in Allied maple group v Simons and Simons  that economic loss has to be speculative and also be real and substantial.
2. Legal causation: legal causation involves considering whether there are any ground upon which the link should be regarded as having been broken. Legal causation has two parts;
Remoteness test which deals with establishing whether the damage was foreseeable to the defendant at the time of the negligence.
Intervening acts, whether after the defendant’s breach any intervening acts broke the chain of causation.
Remoteness: if the consequence of the defendant’s negligence is unforeseeable or they are too remote then the legal causation is not established. This is the rule established in Overseas Tankship (uk) v Morts dock and engineering co. (the wagon mound no-1)  .
prior to the privy council’s above decision it was held in Re Polemis and Furness, withy & co. Ltd  that the defendant would be liable for any consequences of their breach of duty as long as they were directly the result of the breach whether or not these could have been foreseen even if the consequences may have been substantially different from what might be expected by a reasonable person and even if the consequences ended up being for more serious than have been anticipated. The test established in Wagon mound no-1 is now the only test for remoteness of damages in negligence. The wagon mound no-2 did not change the test of wagon mound no-1 but formulated it regarding the foresee ability. it is only the type of damage that needs to have been foreseeable not the extent .on the basis of this principle the House of Lords held in Haghes v Lord Advocate  that it was reasonably foreseeable that the type of damage would be burns therefore the exact means by which the burns occurred did not matter. In Tremain v Pike  injury from rat bites was held foreseeable but disease spreading out of rat’s urine was held not foreseeable.
Egg shell skull rule:
This principle was established in Smith v Leech  .the rule is that due to an existing weakness or frailty if the plaintiff suffers more harm than may be expected then the defendant will be liable for all the damages caused. The maxim is also expressed as the defendant must take the victim as they find them. In Lagden v O’Connor  the principle was confirmed and was held applicable to economic harms. thus if a claimant suffered economic loss as a result of already weak economic circumstances a defendant will be liable for the fall extent of loss.
Intervening Acts: If any event intervenes between the link of defendant’s breach and the claimant’s claim then the defendant will not be liable further for damages suffered from intervening acts. This is the principle of Novus Actus Intervening and there are three types of novus actus events to consider:
Act of God: It includes any thing which is caused by nature and not intervened by human being. The rule is that it will not break the chain of causation if it could have been foreseen by the defendant and he or she should have taken them in to consideration as it was likely to happen. In Jobling v Associated Dairies  the further back injury of the plaintiff was held not foreseeable and as such was considered as the break of chain. In Meah v Mc Creamer (no-1)  it was held that if the later illness can itself be linked to the defendants breach then there will be no break in the chain. In Humber Oil Terminal Trustee Ltd. v Sivand  collapse of the sea bed was not considered as novus actus as it was in the realm of foreseeability.
Act of the claimant: Since the Law reform (contributory negligence) Act 1945, the act of the claimant has been considered as partial defence meaning that the contributory negligence of the plaintiff can be assessed as a proportion and their damages reduced accordingly. But still there some situation exists where the claimant’s own action is so careless that it should remove any share of the responsibility from the original defendant. An example of this is Mc Kew v Holland and Hannen and Cubitt Ltd.  where the claimant’s unreasonable behaviour was considered as the break of chain and the defendant was held not liable. Contrasting to this the court in Wieland v Cyril Lord Carpets  found that the claimant had been as so care full as she could have been and as such it did not break the chain. Surprisingly in a suicidal case the claimant’s own action was found not to break the chain of causation while he was imprisoned  or in police custody  .In Corr v IBC Vehicles  the court also considered the effect of the suicide of the victim.
Act of third party: To break the chain of causation the third party’s act has to be according to Lord Wright “some thing unwarrantable ,a new cause which disturbs the sequence of events ,something which can be described as ……unreasonable or extraneous or extrinsic."  According to Lord Reid, “a subsequent negligent act of a third party must have been some thing very like to happen if it is to be regarded as novus actus intervening breaking the chain of causation ……." 
One of the best known cases is knightly v John  .in this case the negligent traffic control by the police inspector after the accident was considered as a break of chain of causation.
In the case of medical treatment the courts are reluctant to hold that medical treatment breaks the chain of causation unless it is manifestly unreasonable or palpably wrong. The relevant case law is Robinson v The Post office. 
From the above discussion it can be inferred that the modern causation concept in negligence is simply the creation of the court .The court introduced all the rules and case law to secure that justice has to be done. that is why in some respect the court is found very rigid regarding the established rules and principle and in some respect it is found to evade the basic principle where required by justice. From this point of view Lord Steyn’s comment in Chester v Afshar  is definitely the verse of the real fact.