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Cite as: [1987] UKHL 11, [1988] AC 1074, [1988] 1 AC 1074

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JISCBAILII_CASE_TORT

    Parliamentary Archives,
    HL/PO/JU/18/248

    Hilsher (Respondent)

    v.
    Essex Area Health Authority (Appellants)

    JUDGMENT

    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

    HOUSE OF LORDS

    WILSHER
    (RESPONDENT)

    v.

    ESSEX AREA HEALTH AUTHORITY
    (APPELLANTS)

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


    LORD BRIDGE OF HARWICH

    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

    -2 -

    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
    considered.

    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

    - 3 -

    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
    passage:

    "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
    favour.

    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
    RLF.

    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
    ascertained."

    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
    him."

    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
    disease.

    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
    consequences."

    He then referred to the cases of Bonnington Castings Ltd, v.
    Wardlaw
    [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.
    Wardlaw
    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
    one.

    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 -

    LORD FRASER OF TULLYBELTON

    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.

    LORD LOWRY

    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.

    LORD GRIFFITHS

    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.

    LORD ACKNER

    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 -


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