Tort law revision notes on causation. Summary of the key principles and information needed for a university-level tort law exam. Based on lecture notes and textbook reading at the University of Nottingham.
Proving but-for causation by adducing evidence showing that D’s negligence more than
doubled the risk of harm
Per Lord Phillips in Sienkiewicz v Greif (UK) Ltd:
“[72.] The ‘doubles the risk’ test is one that applies epidemiological data to determining causation
on balance of probabilities in circumstances where medical science does not permit determination
with certainty of how and when an injury was caused. The reasoning goes as follows. If statistical
evidence indicates that the intervention of a wrongdoer more than doubled the risk that the victim
would suffer the injury, then it follows that it is more likely than not that the wrongdoer caused the
injury.”
(e.g. there is evidence that 1% of the general population develop a particular cancer as the result of
an exposure to a chemical in the general atmosphere but that 10% of workers in a particular
occupation who are exposed to that chemical at work develop that cancer; it is probable that the
cancer was caused by the exposure at work rather than the exposure in the general atmosphere)
Approach for proving but-for cause when epidemiological evidence is available
Epidemiology = how often diseases occur in different groups of people and why
Epidemiologists collect vast quantities of statistics about incidents and possible causes of
diseases within identified groups of people
Example: comparing the incidents of lung cancer amongst smokers with the incidents of lung
cancer amongst non-smokers – statistics will show that the incidents amongst smokers = higher;
if you are more than twice as likely to get lung cancer if you smoke, it doubles the risk, so it can
be inferred that it was the smoking that caused the lung cancer rather than anything else
Jones v Secretary of State for Energy and Climate Change
The claimant contracted lung disease, partly due to a failing od a statutory duty
However, the secretary of state couldn’t be held liable as he was not twice as likely to have
caused the disease than any other factors
This approach has however been criticised:
o The courts must not adopt a mechanistic statistical approach when using this kind of
evidence
Heneghan v Manchester Dry Docks Ltd.
The claimant was a smoker
Also exposed to asbestos dust through his work with a series of employers
Developed lung cancer
Statistics showed that 0.5% of the general population develop lung cancer
2% of the smokers in the general population also developed lung cancer – this 2% risk was
then increased by over 5 fold for smokers who were exposed to asbestos dust at their place
of work – doubling the risk made it clear that it was probably the asbestos dust that
, caused the lung cancer, not the fact that he was a smoker (both = possible causes for
trigger of lung cancer)
Based on statistics can you decide if one cause is much more likely than the other? – is
statistical evidence is so strong suggesting that one cause is more likely?
Situations where the normal requirements are relaxed in order to achieve justice
Claimant doesn’t need to prove but-for causation
(a) Interpretation of “material contribution”, at least in some cases, as an exception to the but-for
test
Cf Bonnington Castings v Wardlaw – This case can be seen as providing an exception to the but-
for causation test, where it is impossible to prove precisely which one (or more than one)
factor = decisive when you have several factors
See Lord Simon’s explanation of Wardlaw in McGhee v NCB , as establishing a rule that:
Where an injury is caused by two (or more) factors operating cumulatively, of which one (or
more) of the factors is a breach of duty and one (or more) isn’t, and it is impossible to
precisely determine the proportion in which the factors were effective in producing the
injury/which factor was decisive, the claimant is entitled to damages for the injury if he
proves on the balance of probabilities that the breach or breaches of duty contributed
substantially to causing the injury
As long as such factors operate cumulatively, it is immaterial whether they do so
concurrently or successively
Bailey v Ministry of Defence (para 46)
In a case where you cannot prove but-for causation on the balance of probabilities or the
absence of a but-for causation on the balance of probabilities (so situation is uncertain),
where this is because medical science cannot establish but-for causation but can establish
that the contribution of the negligent cause was more than negligible, the but-for test is
modified and the claimant will succeed
Exception to the but-for test
John v Central Manchester Hospitals
Material contribution is not confined to “single agency cases”. Where there are multiple
agencies, the fact that the negligence made a significant contribution to the damage is
enough to establish causation.
In this case, it was impossible to attribute particular damage to a specific cause (3 diff
factors that could have helped to bring about the brain damage). Held that the negligent
delay by the hospital (in ordering CT scan) had materially contributed to the brain damage
and so was enough to hold the defendant liable
Therefore John was entitled to recover in respect of the entirety of his loss. Even though
the claimant couldn’t prove but-for causation, hospital liable + had to pay in damages
, Assuming there is a “material contribution” exception to the but-for test, it only applies to
“disease and clinical negligence cases” and not to claims in private nuisance: Chetwynd v
Tunmore
(b) In some cases it is sufficient to show that D’s wrong materially increased the risk of harm (here,
in an industrial disease case)
McGhee v National Coal Board
To show that a material increase in risk can give rise to liability
Negligent failure of employer to provide a shower for employee working in dusty conditions
materially increased the risk of his developing dermatitis as a result of the dust. Held to be a
sufficient causal connection (approved in Fairchild, below)
The claimant only had to demonstrate that the dust attributable to the breach of duty (the
dust he was exposed to on his journey home) materially increased the risk of him
contracting dermatitis
Employer was found liable in negligence for materially increasing the risk – failure to provide
washing facilities meant that the claimant was exposed to dust for longer than required on
his journey home
Ratio decidendi: Material increase in risk was treated as equivalent to a material
contribution to damage
Wilsher v Essex Area Health Authority
To illustrate multiple causes of damage
Excess of oxygen given negligently to premature baby materially increased the risk of a
blindness condition (RLF)
But there were four other agents that might equally have caused RLF.
Held: causal connection not established (approved in Fairchild, below) – since none of the
potential causes was more likely to have happened than any of the others, the balance of
probabilities was not satisfied
Therefore, taking Bonnington Castings and Wilsher together, where there is more than one
cause, the defendant’s breach must be the substantial cause of the damage
(c) A special rule (the “Fairchild rule”) has been applied where each of a number of defendants in
succession created a risk of harm (here in an industrial disease case)
Fairchild v Glenhaven Funeral Services Ltd [2003]
In a mesothelioma case (indivisible disease) where the claimant had been exposed to
asbestosis at different times while working for different employers, it would be impossible to
satisfy the conventional ‘but-for’ test and prove which exposure was the cause of the
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