Wilsher v Essex Area Health Authority [1987] UKHL 11 (10 March 1987)

Hilsher (Respondent)

Essex Area Health Authority (Appellants)


Die Jovis 10° Martii 1988

Upon Report from the Appellate Committee to whom was
referred the Cause Wilsher against Essex Area Health
Authority, That the Committee had heard Counsel on Monday the
1st, Tuesday the 2nd, Wednesday the 3rd, Thursday the 4th,
Monday the 8th and Tuesday the 9th days of February last, upon
the Petition and Appeal of Essex Area Health Authority, of
Hamstel Road, Harlow, Essex, CM20 1RB, praying that the matter
of the Order set forth in the Schedule thereto, namely an
Order of Her Majesty’s Court of Appeal of the 24th day of July
1986, might be reviewed before Her Majesty the Queen in Her
Court of Parliament and that the said Order might be reversed,
varied or altered or that the Petitioners might have such
other relief in the premises as to Her Majesty the Queen in
Her Court of Parliament might seem meet; as upon the Case of
Martin Graham Wilsher (an infant) lodged by Heather Marjorie
Wilsher, his mother and Next Friend, in answer to the said
Appeal; and due consideration had this day of what was offered
on either side in this Cause:

It is Ordered and Adjudged, by the Lords Spiritual and
Temporal in the Court of Parliament of Her Majesty the Queen
assembled, That the said Order of Her Majesty’s Court of
Appeal (Civil Division) of the 24th day of July 1986 and the
Order of Mr. Justice Peter Pain of the 21st day of December
1984 complained of in the said Appeal be, and the same are
hereby, Set Aside, save as to costs, and that the Cause be,
and the same is hereby, remitted back to the Queen’s Bench
Division of the High Court of Justice with a Direction that
there be a retrial before a different judge of the issue
whether the negligence of the Appellants, as found by the
Court of Appeal, caused or materially contributed to the
Respondent’s retrolental fibroplasia: That the money paid
into Court pursuant to the Order of the Court of Appeal should
remain in Court pending the retrial: And it is further
Ordered, That the costs incurred by the Respondent in respect
of the said Appeal to this House be taxed in accordance with
Schedule 2 to the Legal Aid Act 1974.

Cler: Parliamentor:

Judgment: 10.3.88





Lord Bridge of Harwich
Lord Fraser of Tullybelton
Lord Lowry
Lord Griffiths
Lord Ackner


My Lords,

The infant plaintiff was born nearly three months
prematurely on 15 December 1978. He weighed only 1200
grammes. In the first few weeks of life he suffered from most of
the afflictions which beset premature babies. He passed through a
series of crises and very nearly died. The greatest danger which
faces the very premature baby, on account of the imperfect
function of incompletely developed lungs, is death or brain damage
from failure of the oxygen supply to the brain. That Martin not
only survived but also now retains unimpaired brain function is due
both to the remarkable advances of medical science and technology
in this field in comparatively recent years and to the treatment he
received in the special baby care unit of the Princess Alexandra
Hospital, Harlow.

Tragically, however, he succumbed to another well-known
hazard of prematurity. He suffers from retrolental fibroplasia
(RLF), an incurable condition of the retina which, in his case, has
caused total blindness in one eye and severely impaired vision in
the other. He sued the Essex Area Health Authority (“the
authority”) who are responsible for the Princess Alexandra Hospital,
Harlow, on the ground that his RLF was caused by an excess of
oxygen tension in his bloodstream in the early weeks attributable
to a want of proper skill and care in the management of his
oxygen supply. The action was heard by Peter Pain J. and the
trial lasted 20 days. In addition to the evidence of the medical
and nursing staff at the hospital, the judge heard expert evidence
from two paediatricians and two ophthalmologists called for the
plaintiff and from three paediatricians and one ophthalmologist
called for the authority. All were highly qualified and
distinguished experts in their respective fields. In addition, no less
than 24 articles from medical journals about RLF covering 129
foolscap pages of print were put in evidence.

The allegations of negligence against the authority related
to two quite distinct phases of Martin’s treatment. The first
concerned the first 38 hours after his birth. In order to monitor
the partial pressure of oxygen (PO2) in the arterial blood of a
premature baby, it is standard practice to pass a catheter through
the umbilical artery into the aorta. This enables the PO2 to be
measured in two ways. At the tip of the catheter is an electronic
sensor connected to a monitor outside the body which, if correctly
calibrated, should give an accurate reading of the PO2. In
addition, an aperture in the catheter close to the sensor enables
samples of blood to be taken for conventional blood analysis at
regular intervals to check and, if necessary, adjust the monitor’s
calibration. Again it is standard practice to check the location of
the sensor by X-ray after the catheter has been inserted. In
Martin’s case the catheter was inserted by mistake into a vein
instead of an artery so that the sensor and the sampling aperture
were wrongly located in the heart instead of the aorta. This
meant that they would sample a mixture of arterial and venous
blood instead of pure arterial blood, which would consequently give
a false reading of the level of PO2 in the arterial blood. The
house officer and the registrar who were on duty at the material
time and who saw the X-ray which was taken both failed to notice
the mistake. The judge held this failure to amount to negligence
for which the authority were liable. The plaintiff’s case in
relation to this first allegation of negligence was that the
misplaced catheter gave readings of PO2 well below the true level
of PO2 in the arterial blood which led to excessive administration
of oxygen in an attempt to raise the PO2 level and that in
consequence the true PO2 level was excessively high for a
substantial period until the mislocation of the catheter was
realised at 8 o’clock on the morning of 17 December 1978.

A second phase of Martin’s treatment alleged to have been
negligent was between 20 December 1978 and 23 January 1979.
Between these dates it was alleged that there were five distinct
periods of differing duration when the medical and nursing staff
responsible for Martin’s care were in breach of duty in allowing
the level of PO2 in his arterial blood to remain above the
accepted level of safety. The judge found that four of these five
periods of exposure to an unduly high level of PO2 were due to
the authority’s negligence.

In making his finding of negligence in relation to each of
the periods of raised PO2 levels except the first attributable to
the misplaced catheter, the judge relied upon a principle of law
which he thought was laid down by this House in McGhee v.
National Coal Board
 [1973] 1 WLR 1 and which he had stated in
his own earlier decision in Clark v. MacLennan [1983] 1 A11.E.R.
416, 427 in the following terms:

“It seems to me that it follows from McGhee that where
there is a situation in which a general duty of care arises
and there is a failure to take a precaution, and that very
damage occurs against which the precaution is designed to
be a protection, then the burden lies on the defendant to

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show that he was not in breach of duty as well as to show
that the damage did not result from his breach of duty.”

The judge thought that this proposition of law derived support
from the decision at first instance of Mustill J. in Thompson v.
Smiths Shiprepairers (North Shields) Ltd. [1984] Q.B. 405. He held
that the authority had failed to prove on a balance of probabilities
either that they were not negligent or that their negligence did
not cause or materially contribute to Martin’s RLF. He therefore
held them liable in damages and gave judgment for the plaintiff
for £116,199.14.

The Court of Appeal (Sir Nicolas Browne-Wilkinson, V.-C.,
Mustill and Glidewell L.JJ) affirmed this judgment by a majority,
the Vice-Chancellor dissenting [1987] 1 Q.B. 730. They gave leave
on terms to the authority to appeal to this House. A number of
issues were argued in the Court of Appeal. They unanimously
affirmed the finding of negligence against the authority, though by
marginally different processes of reasoning, on the ground of the
authority’s vicarious liability for the registrar’s failure to observe
from the X-ray that the first catheter inserted into Martin’s
umbilicus was located in a vein not in an artery. They
unanimously reversed the judges’ finding of negligence in relation
to the later periods when the level of PO2 in Martin’s blood was
raised on the ground that he had misdirected himself in holding
that the burden of proof was reversed so that it lay upon the
authority to show that they were not negligent. On examination
of the evidence the Court of Appeal found that no negligence was
established in relation to these later periods. No issue arises in
the present appeal to your Lordships’ House in respect of either of
these conclusions on liability and nothing more need be said about
them. The crucial issue which now arises and on which the Court
of Appeal were divided in their opinions is whether the judgment
can be affirmed on the ground that any raised level of PO2 in
Martin’s arterial blood before 8 o’clock on the morning or 17
December 1978 consequent on misplacement of the catheter caused
or materially contributed to Martin’s RLF.

My Lords, I understand that all your Lordships agree that
this appeal has to be allowed and that the inevitable consequence
of this is that the outstanding issue of causation must, unless the
parties can reach agreement, be retried by another judge. In
these circumstances, for obvious reasons, it is undesirable that I
should go into the highly complex and technical evidence on which
the issue depends any further than is strictly necessary to explain
why, in common with all your Lordships, I feel ineluctably driven
to the unpalatable conclusion that it is not open to the House to
resolve the issue one way or the other, so that a question
depending on the consequence of an event occurring in the first
two days of Martin’s life will now have to be investigated all over
again when Martin is nearly ten years old. On the other hand, the
appeal raises a question of law as to the proper approach to issues
of causation which is of great importance and of particular
concern in medical negligence cases. This must be fully

There was in the voluminous expert evidence given at the
trial an irreconcilable conflict of opinion as to the cause of
Martin’s RLF. It was common ground that a sufficiently high

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level of PO2 in the arterial blood of a very premature baby, if
maintained for a sufficiently long period of time, can have a toxic
effect on the immature blood vessels in the retina leading to a
condition which may either regress or develop into RLF. It was
equally common ground, however, that RLF may occur in
premature babies who have survived without any artificial
administration of oxygen and that there is evidence to indicate a
correlation between RLF and a number of other conditions from
which premature babies commonly suffer (e.g. apnoeia, hypercarbia,
intraventricular haemorrhage, patent ductus arteriosus, all
conditions which afflicted Martin) although no causal mechanisms
linking these conditions with the development of RLF have been
positively identified. However, what, if any, part artificial
administration of oxygen causing an unduly high level of PO2 in
Martin’s arterial blood played in the causation of Martin’s RLF
was radically in dispute between the experts. There was certainly
evidence led in support of the plaintiff’s case that high levels of
PO2 in general and, more particularly, the level of PO2 maintained
when the misplaced catheter was giving misleadingly low readings
of the level in the arterial blood were probably at least a
contributory cause of Martin’s RLF. If the judge had directed
himself that it was for the plaintiff to discharge the onus of
proving causation on a balance of probabilities and had indicated
his acceptance of this evidence in preference to the contrary
evidence led for the authority, a finding in favour of the plaintiff
would have been unassailable. That is why it is conceded by Mr.
Henry Brooke Q.C., for the authority, that the most he can ask
for, if his appeal succeeds, is an order for retrial of the causation
issue. However, the burden of the relevant expert evidence led
for the authority, to summarise it in very general terms, was to
the effect that any excessive administration of oxygen which
resulted from the misplacement of the catheter did not result in
the PO2 in the arterial blood being raised to a sufficiently high
level for a sufficient length of time to have been capable of
playing any part in the causation of Martin’s RLF. One of the
difficulties is that, underlying this conflict of medical opinion,
there was not only a profound difference of view about the
aetiology and causation of RLF in general but also a substantial
difference as to the inferences which were to be drawn from the
primary facts, as ascertained from the clinical notes about
Martin’s condition and treatment at the material time and
amplified by the oral evidence of Dr. Wiles, the senior house
officer in charge, as to what the actual levels of PO2 in Martin’s
arterial blood were likely to have been during a critical period
between 10 p.m. on 16 December when Martin was first being
administered pure oxygen through a ventilator and 8 a.m. the next
morning when, after discovery of the mistake about the catheter,
the level of oxygen administration was immediately reduced.

Having found the authority negligent in relation to the five
periods when the PO2 level was unduly high, the judge added:

“There is no dispute that this materially increased the risk
of RLF.”

This statement, it is now accepted, was a misunderstanding
of the evidence. Whilst it was common ground that one of the
objects of monitoring and controlling the PO2 level in the arterial
blood of a premature baby in 1978 was to avoid or reduce the risk

– 4 –

of RLF, it was certainly not accepted by the defence that any of
the levels to which Martin was subjected were sufficient in degree
or duration to have involved any material increase in that risk.
This misunderstanding was one of the factors which led the judge
to the conclusion that Martin had established a prima facie case
on the issues of causation. He then said:

“But it is open to the defendants on the facts of this case
to show that they are not liable for this negligence because
on the balance of probability this exposure did not cause
Martin’s RLF.”

It was on this premise that the judge examined the issue of
causation. In a judgment which runs to 68 pages of transcript,
only two and a half pages are devoted to this issue. The judge
repeatedly emphasised that the onus was on the authority, saying
at one point:

“For the purpose of this action I need go no further than to
consider whether the breaches have probably made no
substantial contribution to the plaintiff’s condition.”

And, again, a little later on:

“So I have to consider whether the exposure that occurred
probably did no harm.”

After a brief reference to the evidence of one of the
plaintiff’s witnesses and one of the authority’s witnesses whose
answers were based on an assumption of fact which he was invited
to make, the judge expressed his conclusion in the following

“On the basis of this evidence I find that the defendants
fail to show that the first and third periods of exposure did
not do any damage; indeed the probability is that they did.
As to the second, fourth and fifth periods the position is
more doubtful. The trouble is the lack of data. The blood
gas readings were not sufficiently frequent to enable us to
assess whether the excessively high readings were a peak or
whether they indicate a longer period; indeed, it is possible
that the true figure went higher. The defendants, in my
view, have failed to show that these periods did not cause
or materially contribute to Martin’s RLF.” (My emphasis)

Mr. David Latham Q.C., seeking to uphold the judgment in
Martin’s favour, naturally relied heavily on the words I have
emphasised in this passage and pointed to the contrast between the
judge’s view, thereby expressed, of the causative effect of what is
now the only relevant period of exposure calling for consideration
and his doubts about the effect of three of the four later periods.
He urged your Lordships to read this as an indication by the judge
that, if he had held the onus to lie on the plaintiff, he would have
found it discharged on a balance of probabilities. The Court of
Appeal did not feel able to accede to a similar submission and I
agree with them. As Mustill L.J. pointed out [1987] 1 Q.B. 730,
763G, the judge expressed no preference for the plaintiff’s experts
on this point. Moreover, it is inconceivable that this very careful
judge, if he had directed himself that the burden of proof lay on

– 5 –

the plaintiff, would not have subjected the complex and conflicting
evidence to a thorough scrutiny and analysis before committing
himself to an orthodox finding of causation in the plaintiff’s

Both parties accepted that the conflict of evidence was of
such a nature that it could not properly be resolved by your
Lordships simply reading the transcript. Indeed, we were not
asked to examine the totality of the voluminous medical evidence.
Just as Mr. Brooke accepted that it was not open to the House to
dismiss the plaintiff’s claim, so Mr. Latham accepted that, if he
failed in the submission which I have examined and rejected in the
foregoing paragraph, he could not invite the House to make an
independent finding in the plaintiff’s favour on the simple basis
that the expert evidence on a balance of probabilities affirmatively
established causation.

The Court of Appeal, although they felt unable to resolve
the primary conflict in the expert evidence as to the causation of
Martin’s RLF, did make a finding that the levels of PO2 which
Martin experienced in consequence of the misplacement of the
catheter were of a kind capable of causing RLF. Mustill L.J. at
p. 766D expressed his anxiety as to whether “by making a further
finding on an issue where there was a sharp conflict between the
expert witnesses, we are not going too far in the effort to avoid a
retrial.” But he concluded at p. 766E that it was “legitimate,
after reading and re-reading the evidence,” to make this finding
based on “the weight of the expert evidence.” This finding by the
Court of Appeal is challenged by Mr. Brooke, for the authority, as
one which it was not open to them to make. I must return to
this issue later. But assuming, as I do for the present, that the
finding was properly made, it carried the plaintiff’s case no
further than to establish that oxygen administered to Martin as a
consequence of the negligent failure to detect the misplacement of
the catheter was one of a number of possible causes of Martin’s

Mustill L.3. subjected the speeches in McGhee v. National
Coal Board
 [1973] 1 WLR 1 to a careful scrutiny and analysis
and concluded that they established a principle of law which he
expressed in the following terms at pp. 771-772:

“If it is an 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
two parties stand in such a relationship that the one party
owes a duty not to conduct himself in that way; and if the
first party does 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

Applying this principle to the finding that the authority’s
negligence was one of the possible causes of Martin’s RLF, he held
that this was sufficient to enable the court to conclude that the
negligence was “taken to have caused the injury.” Glidewell L.J.
reached the same conclusion by substantially the same process of
reasoning. The Vice-Chancellor took the opposite view.

– 6 –

The starting point for any consideration of the relevant law
of causation is the decision of this House in Bonnington Castings
Ltd, v. Wardlaw
 [1956] AC 613. This was the case of a pursuer
who, in the course of his employment by the defenders, contracted
pneumoconiosis over a period of years by the inhalation of invisible
particles of silica dust from two sources. One of these (pneumatic
hammers) was an “innocent” source, in the sense that the pursuer
could not complain that his exposure to it involved any breach of
duty on the part of his employers. The other source, however,
(swing grinders) arose from a breach of statutory duty by the
employer. Delivering the leading speech in the House Lord Reid
said at pp. 619-620:

“The Lord Ordinary and the majority of the First Division
have dealt with this case on the footing that there was an
onus on the defenders, the appellants, to prove that the dust
from the swing grinders did not cause the pursuer’s disease.
This view was based on a passage in the judgment of the
Court of Appeal in Vyner v. Waldenberg Brothers Ltd. [1946]
K.B. 50: ‘If there is a definite breach of a safety provision
imposed on the occupier of a factory, and a workman is
injured in a way which could result from the breach, the
onus of proof shifts on to the employer to show that the
breach was not the cause. We think that that principle lies
at the very basis of statutory rules of absolute duty’ (per
Scott L.J. at p. 55). … Of course, the onus was on the
defendants to prove delegation (if that was an answer) and
to prove contributory negligence, and it may be that that is
what the Court of Appeal had in mind. But the passage
which I have cited appears to go beyond that, and, in so far
as it does so, I am of opinion that it is erroneous.

It would seem obvious in principle that a pursuer or plaintiff
must prove not only negligence or breach of duty but also
that such fault caused or materially contributed to his
injury, and there is ample authority for that proposition both
in Scotland and in England. I can find neither reason nor
authority for the rule being different where there is breach
of a statutory duty. The fact that Parliament imposes a
duty for the protection of employees has been held to
entitle an employee to sue if he is injured as a result of a
breach of that duty, but it would be going a great deal
farther to hold that it can be inferred from the enactment
of a duty that Parliament intended that any employee
suffering injury can sue his employer merely because there
was a breach of duty and it is shown to be possible that his
injury may have been caused by it. In my judgment, the
employee must in all cases prove his case by the ordinary
standard of proof in civil actions; he must make it appear
at least that on a balance of probabilities the breach of
duty caused or materially contributed to his injury.”

Lord Tucker said of Scott L.J.’s dictum in Vyner v. Waldenberg
Brothers Ltd.,
 at pp. 624-625:

‘I think it is desirable that your Lordships should take this
opportunity to state in plain terms that no such onus exists
unless the statute or statutory regulation expressly or

 7 –

impliedly so provides, as in several instances it does. No
distinction can be drawn between actions for common law
negligence and actions for breach of statutory duty in this
respect. In both the plaintiff or pursuer must prove (a)
breach of duty and (b) that such breach caused the injury
complained of – (See Wakelin v. London and South Western
Railway Co.
 (1886) 12 App. Cas. 41 and Caswell v. Powell
Duffryn Associated Collieries
 [1940] A.C. 152). In each case
it will depend upon the particular facts proved and the
proper inferences to be drawn therefrom whether the
pursuer has sufficiently discharged the onus that lies upon

Lord Keith of Avonholm said at p. 625:

“The onus is on the pursuer to prove his case, and I see no
reason to depart from this elementary principle by invoking
certain rules of onus said to be based on a correspondence
between the injury suffered and the evil guarded against by
some statutory regulation. I think most, if not all, of the
cases which professed to lay down or to recognise some
such rule could have been decided as they were on simple
rules of evidence, and I agree that the case of Vyner [1946]
K.B. 50, in so far as it professed to enunciate a principle of
law inverting the onus of proof cannot be supported.”

Viscount Simonds and Lord Somervell of Harrow agreed.

Their Lordships concluded, however, from the evidence that
the inhalation of dust to which the pursuer was exposed by the
defenders’ breach of statutory duty had made a material
contribution to his pneumoconiosis which was sufficient to
discharge the onus on the pursuer of proving that his damage was
caused by the defenders’ tort.

A year later the decision in Nicholson v. Atlas Steel
Foundry and Engineering Co. Ltd. [1957] 1 W.L.R. 613 followed the
decision in Bonnington Castings Ltd, v. Wardlaw and held, in
another case of pneumoconiosis, that the employers were liable for
the employee’s disease arising from the inhalation of dust from
two sources, one “innocent” the other “guilty,” on facts virtually
indistinguishable from those in the case of Bonnington Castings
Ltd. v. Wardlaw.

In McGhee v. National Coal Board [1973] 1 WLR 1 the
pursuer worked in a brick kiln in hot and dusty conditions in which
brick dust adhered to his sweaty skin. No breach of duty by his
employers, the defenders, was established in respect of his working
conditions. However, the employers were held to be at fault in
failing to provide adequate washing facilities which resulted in the
pursuer having to bicycle home after work with his body still
caked in brick dust. The pursuer contracted dermatitis and the
evidence that this was caused by the brick dust was accepted.
Brick dust adhering to the skin was a recognised cause of
industrial dermatitis and the provision of showers to remove it
after work was a usual precaution to minimise the risk of the
disease. The precise mechanism of causation of the disease,
however, was not known and the furthest the doctors called for
the pursuer were able to go was to say that the provision of

– 8 –

showers would have materially reduced the risk of dermatitis.
They were unable to say that it would probably have prevented the

The pursuer failed before the Lord Ordinary and the First
Division of the Court of Session on the ground that he had not
discharged the burden of proof of causation. He succeeded on
appeal to the House of Lords. Much of the academic discussion to
which this decision has given rise has focussed on the speech of
Lord Wilberforce, particularly on two paragraphs. He said at p. 6:

“But the question remains whether a pursuer must
necessarily fail if, after he has shown a breach of duty,
involving an increase of risk of disease, he cannot positively
prove that this increase of risk caused or materially
contributed to the disease while his employers cannot
positively prove the contrary. In this intermediate case
there is an appearance of logic in the view that the
pursuer, on whom the onus lies, should fail – a logic which
dictated the judgments below. The question is whether we
should be satisfied in factual situations like the present,
with this logical approach. In my opinion, there are further
considerations of importance. First, it is a sound principle
that where a person has, by breach of a duty of care,
created a risk, and injury occurs within the area of that
risk, the loss should be borne by him unless he shows that it
had some other cause.
 Secondly, from the evidential point
of view, one may ask, why should a man who is able to
show that his employer should have taken certain
precautions, because without them there is a risk, or an
added risk, of injury or disease, and who in fact sustains
exactly that injury or disease, have to assume the burden of
proving more; namely, that it was the addition to the risk,
caused by the breach of duty, which caused or materially
contributed to the injury? In many cases, of which the
present is typical, this is impossible to prove, just because
honest medical opinion cannot segregate the causes of an
illness between compound causes. And if one asks which of
the parties, the workman or the employers should suffer
from this inherent evidential difficulty, the answer as a
matter in policy or justice should be that it is the creator
of the risk who, ex hypothesi must be taken to have
foreseen the possibility of damage, who should bear its

He then referred to the cases of Bonnington Castings Ltd, v.
 [1956] AC 613 and Nicholson v. Atlas Steel Foundry and
Engineering Co. Ltd.
 [1957] 1 W.L.R. 613 and added at p. 7:

“The present factual situation has its differences: the
default here consisted not in adding a material quantity to
the accumulation of injurious particles but by failure to take
a step which materially increased the risk that the dust
already present would cause injury. And I must say that, at
least in the present case, to bridge the evidential gap by
inference seems to me something of a fiction, since it was
precisely this inference which the medical expert declined to
make. But I find in the cases quoted an analogy which
suggests the conclusion that, in the absence of proof that

– 9 –

the culpable addition had, in the result, no effect, the
employers should be liable for an injury, squarely within the
risk which they created and that they, not the pursuer,
should suffer the consequence of the impossibility,
foreseeably inherent in the nature of his injury, of
segregating the precise consequence of their default.” (I
have added the emphasis in both these two passages.)

My Lords, it seems to me that both these paragraphs,
particularly in the words I have emphasised, amount to saying that,
in the circumstances, the burden of proof of causation is reversed
and thereby to run counter to the unanimous and emphatic opinions
expressed in Bonnington Castings Ltd, v. Wardlaw [1956] AC 613
to the contrary effect. I find no support in any of the other
speeches for the view that the burden of proof is reversed and, in
this respect, I think Lord Wilberforce’s reasoning must be regarded
as expressing a minority opinion.

A distinction is, of course, apparent between the facts of
Bonnington Castings Ltd, v. Wardlaw, where the “innocent” and
“guilty” silica dust particles which together caused the pursuer’s
lung disease were inhaled concurrently and the facts of McGhee v.
National Coal Board
 [1973] 1 WLR 1 where the “innocent” and
“guilty” brick dust was present on the pursuer’s body for
consecutive periods. In the one case the concurrent inhalation of
“innocent” and “guilty” dust must both have contributed to the
cause of the disease. In the other case the consecutive periods
when “innocent” and “guilty” brick dust was present on the
pursuer’s body may both have contributed to the cause of the
disease or, theoretically at least, one or other may have been the
sole cause. But where the layman is told by the doctors that the
longer the brick dust remains on the body, the greater the risk of
dermatitis, although the doctors cannot identify the process of
causation scientifically, there seems to be nothing irrational in
drawing the inference, as a matter of common sense, that the
consecutive periods when brick dust remained on the body probably
contributed cumulatively to the causation of the dermatitis. I
believe that a process of inferential reasoning on these general
lines underlies the decision of the majority in McGhee’s case.

In support of this view, I refer to the following passages.
Lord Reid said at pp. 3-4:

“The medical witnesses are in substantial agreement.
Dermatitis can be caused, and this dermatitis was caused,
by repeated minute abrasion of the outer horny layer of the
skin followed by some injury to or change in the underlying
cells, the precise nature of which has not yet been
discovered by medical science. If a man sweats profusely
for a considerable time the outer layer of his skin is
softened and easily injured. If he is then working in a
cloud of abrasive brick dust, as this man was, the particles
of dust will adhere to his skin in considerable quantity and
exertion will cause them to injure the horny layer and
expose to injury or infection the tender cells below. Then
in some way not yet understood dermatitis may result.

If the skin is not thoroughly washed as soon as the man
ceases work that process can continue at least for some

– 10 –

considerable time. This man had to continue exerting
himself after work by bicycling home while still caked with
sweat and grime, so he would be liable to further injury
until he could wash himself thoroughly. Washing is the only
practicable method of removing the danger of further injury.

The effect of such abrasion of the skin is cumulative in the
sense that the longer a subject is exposed to injury the
greater the chance of his developing dermatitis: it is for
that reason that immediate washing is well recognised as a
proper precaution.”

He concluded at pp. 4-5:

“The medical evidence is to the effect that the fact that
the man had to cycle home caked with grime and sweat
added materially to the risk that this disease might develop.
It does not and could not explain just why that is so. But
experience shows that it is so. Plainly that must be
because what happens while the man remains unwashed can
have a causative effect, though just how the cause operates
is uncertain. I cannot accept the view expressed in the
Inner House that once the man left the brick kiln he left
behind the causes which made him liable to develop
dermatitis. That seems to me quite inconsistent with a
proper interpretation of the medical evidence. Nor can I
accept the distinction drawn by the Lord Ordinary between
materially increasing the risk that the disease will occur and
making a material contribution to its occurrence.

There may be some logical ground for such a distinction
where our knowledge of all the material factors is complete.
But it has often been said that the legal concept of
causation is not based on logic or philosophy. It is based on
the practical way in which the ordinary man’s mind works in
the everyday affairs of life. From a broad and practical
viewpoint I can see no substantial difference between saying
that what the defender did materially increased the risk of
injury to the pursuer and saying that what the defender did
made a material contribution to his injury.”

Lord Simon of Glaisdale said at p. 8:

“But Bonnington Castings Ltd, v. Wardlaw [1956] AC 613
and Nicholson v. Atlas Steel Foundry Engineering Co. Ltd.
[1957] 1 W.L.R. 613 establish, in my view, that where an
injury is caused by two (or more) factors operating
cumulatively, one (or more) of which factors is a breach of
duty and one (or more) is not so, in such a way that it is
impossible to ascertain the proportion in which the factors
were effective in producing the injury or which factor was
decisive, the law does not require a pursuer or plaintiff to
prove the impossible, but holds that he is entitled to
damages for the injury if he proves on a balance of
probabilities that the breach or breaches of duty contributed
substantially to causing the injury. If such factors so
operate cumulatively, it is, in my judgment, immaterial
whether they do so concurrently or successively.”

Lord Kilbrandon said at p. 10:

– 11 –

“In the present case, the pursuer’s body was vulnerable,
while he was bicycling home, to the dirt which had been
deposited on it during his working hours. It would not have
been if he had had a shower. If showers had been provided
he would have used them. It is admittedly more probable
that disease will be contracted if a shower is not taken. In
these circumstances I cannot accept the argument that
nevertheless it is not more probable than not that, if the
duty to provide a shower had not been neglected, he would
not have contracted the disease. The pursuer has after all,
only to satisfy the court of a probability, not to
demonstrate an irrefragable chain of causation, which in a
case of dermatitis, in the present state of medical
knowledge, he could probably never do.”

Lord Salmon said at pp. 11-12:

“I, of course, accept that the burden rests upon the pursuer
to prove, on a balance of probabilities, a causal connection
between his injury and the defenders’ negligence. It is not
necessary, however, to prove that the defenders’ negligence
was the only cause of injury. A factor, by itself, may not
be sufficient to cause injury but if, with other factors, it
materially contributes to causing injury, it is clearly a cause
of injury. Everything in the present case depends upon what
constitutes a cause. I venture to repeat what I said in
Alphacell Ltd, v. Woodward [1972] AC 824, 847: ‘The
nature of causation has been discussed by many eminent
philosophers and also by a number of learned judges in the
past. I consider, however, that what or who has caused a
certain event to occur is essentially a practical question of
fact which can best be answered by ordinary commonsense
rather than abstract metaphysical theory.’ In the

circumstances of the present case it seems to me unrealistic
and contrary to ordinary commonsense to hold that the
negligence which materially increased the risk of injury did
not materially contribute to causing the injury.”

Then after referring to the cases of Bonnington Castings Ltd, v.
 and Nicholson he added at pp. 12-13:

“I do not find the attempts to distinguish those authorities
from the present case at all convincing. In the
circumstances of the present case, the possibility of a
distinction existing between (a) having materially increased
the risk of contracting the disease, and (b) having materially
contributed to causing the disease may no doubt be a
fruitful source of interesting academic discussions between
students of philosophy. Such a distinction is, however, far
too unreal to be recognised by the common law.”

The conclusion I draw from these passages is that McGhee
v. National Coal Board
 [1973] 1 WLR 1 laid down no new
principle of law whatever. On the contrary, it affirmed the
principle that the onus of proving causation lies on the pursuer or
plaintiff. 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 defenders’

– 12 –

negligence had materially contributed to the pursuer’s injury. The
decision, in my opinion, is of no greater significance than that and
the attempt to extract from it some esoteric principle which in
some way modifies, as a matter of law, the nature of the burden
of proof of causation which a plaintiff or pursuer must discharge
once he has established a relevant breach of duty is a fruitless

In the Court of Appeal in the instant case Sir Nicolas
Browne-Wilkinson V.-C., being in a minority, expressed his view on
causation with understandable caution. But I am quite unable to
find any fault with the following passage in his dissenting judgment
[1987] Q.B. 730, 779:

“To apply the principle in McGhee v. National Coal Board
[1973] 1 WLR 1 to the present case would constitute an
extension of that principle. In the McGhee case there was
no doubt that the pursuer’s dermatitis was physically caused
by brick dust: the only question was whether the continued
presence of such brick dust on the pursuer’s skin after the
time when he should have been provided with a shower
caused or materially contributed to the dermatitis which he
contracted. There was only one possible agent which could
have caused the dermatitis, viz., brick dust, and there was
no doubt that the dermatitis from which he suffered was
caused by that brick dust.

In the present case the question is different. There are a
number of different agents which could have caused the
RLF. Excess oxygen was one of them. The defendants
failed to take reasonable precautions to prevent one of the
possible causative agents (e.g. excess oxygen) from causing
RLF. But no one can tell in this case whether excess
oxygen did or did not cause or contribute to the RLF
suffered by the plaintiff. The plaintiff’s RLF may have
been caused by some completely different agent or agents,
e.g. hypercarbia, intraventricular haemorrhage, apnoea or
patent ductus arteriosus. In addition to oxygen, each of
those conditions has been implicated as a possible cause of
RLF. This baby suffered from each of those conditions at
various times in the first two months of his life. There is
no satisfactory evidence that excess oxygen is more likely
than any of those other five candidates to have caused RLF
in this baby. To my mind, the occurrence of RLF following
a failure to take a necessary precaution to prevent excess
oxygen causing RLF provides no evidence and raises no
presumption that it was excess oxygen rather than one or
more of the five other possible agents which caused or
contributed to RLF in this case.

The position, to my mind, is wholly different from that in
the McGhee case where there was only one candidate (brick
dust) which could have caused the dermatitis and failure to
take a precaution against brick dust causing dermatitis was
followed by dermatitis caused by brick dust. In such a
case, I can see the common sense, if not the logic, of
holding that, in the absence of any other evidence, the
failure to take the precaution caused or contributed to the
dermatitis. To the extent that certain members of the

– 13 –

House of Lords decided the question on inference from
evidence or presumptions, I do not consider that the present
case falls within their reasoning. A failure to take
preventative measures against one out of six possible causes
is no evidence as to which of those six caused the injury.”

Since, on this view, the appeal must, in any event, be
allowed, it is not strictly necessary to decide whether it was open
to the Court of Appeal to resolve one of the conflicts between
the experts which the judge left unresolved and to find that the
oxygen administered to Martin in consequence of the misleading
PO2 levels derived from the misplaced catheter was capable of
having caused or materially contributed to his RLF. I very well
understand the anxiety of the majority to avoid the necessity for
ordering a retrial if that was at all possible. But having accepted,
as your Lordships and counsel have had to accept, that the
primary conflict of opinion between the experts as to whether
excessive oxygen in the first two days of life probably did cause
or materially contribute to Martin’s RLF cannot be resolved by
reading the transcript, I doubt, with all respect, if the Court of
Appeal were entitled to try to resolve the secondary conflict as to
whether it could have done so. Where expert witnesses are
radically at issue about complex technical questions within their
own field and are examined and cross-examined at length about
their conflicting theories, I believe that the judge’s advantage in
seeing them and hearing them is scarcely less important than when
he has to resolve some conflict of primary fact between lay
witnesses in purely mundane matters. So here, in the absence of
relevant findings of fact by the judge, there was really no
alternative to a retrial. At all events, the judge who retries the
issue of causation should approach it with an entirely open mind
uninfluenced by any view of the facts bearing upon causation
expressed in the Court of Appeal.

To have to order a retrial is a highly unsatisfactory result
and one cannot help feeling the profoundest sympathy for Martin
and his family that the outcome is once again in doubt and that
this litigation may have to drag on. Many may feel that such a
result serves only to highlight the shortcomings of a system in
which the victim of some grievous misfortune will recover
substantial compensation or none at all according to the
unpredictable hazards of the forensic process. But, whether we
like it or not, the law, which only Parliament can change, requires
proof of fault causing damage as the basis of liability in tort. We
should do society nothing but disservice if we made the forensic
process still more unpredictable and hazardous by distorting the
law to accommodate the exigencies of what may seem hard cases.

Leave to appeal was given by the Court of Appeal on terms
that the authority should not seek an order for costs in this House
or for variation of the orders for costs in the courts below. For
the reasons I have indicated I would allow the appeal, set aside
the order of the Court of Appeal save as to costs and order
retrial of the issue whether the negligence of the authority, as
found by the Court of Appeal, caused or materially contributed to
the plaintiff’s RLF.

– 14 –


My Lords,

I have had the advantage of reading in draft the speech of
my noble and learned friend Lord Bridge of Harwich and I entirely
agree with it. For the reasons stated in it I would allow the
appeal and make an order in the terms proposed by my noble and
learned friend.


My Lords,

I have had the opportunity of reading in draft the speech of
my noble and learned friend Lord Bridge of Harwich. I agree with
it and accordingly concur in his conclusions and in the order which
he proposes.


My Lords,

I have had the advantage of reading in draft the speech
prepared by my noble and learned friend Lord Bridge of Harwich.
I agree with it and the order which he proposes.


My Lords,

I have had the advantage of reading in draft the speech of
my noble and learned friend Lord Bridge of Harwich. I agree with
it and the order which he proposes.

– 15 –

Source: https://www.bailii.org/