Nursing Law and Ethics

6.4.3 Causation: material contribution

Sometimes it will be impossible for the experts to say that the defendant's default
has, on the balance of probabilities, caused the damage, but they may be able to say
on the balance of probabilities that the default has materially contributed to the
damage. Where this is the case, the claimant is entitled to succeed in full.
An example isBonnington Castingsv.Wardlaw1956). The claimant there was a
steel dresser. In the course of his work he was exposed to silica dust from two
sources. The exposure to dust from one source was a consequence of the defen-
dant's breach of statutory duty; the exposure to dust from the other was not. He
developed pneumoconiosis. It was impossible to determine the contribution
which the guilty dust' and theinnocent dust' had made to his disease. All that
could be said was that the contribution made by the `guilty dust' was notde
minimis.Those facts, said the House of Lords, meant that the claimant was entitled
to judgment for damages representing all his illness and its financial
consequences. Lord Reid said:

`... I cannot agree that the question is: which was the most probable source of

the [claimant's] disease, the [`innocent dust'] or the [`guilty dust']? It appears to

me that the source of his disease was the dust from both sources, and the real

question is whether the [`guilty dust'] materially contributed to the disease.

What is a material contribution must be a question of degree. Acontribution

which comes within the exceptionde minimis non curat lexis not material, but I

think that any contribution which does not fall within that exception must be

material. I do not see how there can be something too large to come within thede

minimisprinciple but yet too small to be material.' p. 621)

The House of Lords appeared to extend this principle inMcGheev.National Coal
Board1972). They said there that where the defendant's default had materially
increased the risk of the injury which in fact occurred, the claimant succeeded in
full. This case produced uproar among practitioners and academics. It was pointed
out that if all you could do was to prove a material contribution to risk, you had
failed to prove that there was anything causative about the defendant's default at
all. Judges were extremely reluctant to followMcGhee,but it haunted the law of tort
until it was exorcised by the House of Lords inWilsherv.Essex AHA1986). In
WilsherLord Bridge said:

`McGhee...laid down no new principle of law whatever. On the contrary, it

affirmed the principle that the onus of proving causation lies on the [claimant].

Adopting a robust and pragmatic approach to the undisputed primary facts of

the case, the majority concluded that it was a legitimate inference of fact that the

[defendant's] negligence had materially contributed to the [claimant's] injury.

The decision, in my opinion, is of no greater significance than that...' pp.

881±2)

Whenever the House of Lords describes the decision of a differently constituted
House as `robust and pragmatic' it is clear that there is deep intellectual embar-
rassment. The fact is thatMcGheewas plainly wrong.
It is surprising how seldom theBonnington Castingsprinciple is wielded in

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