Breach of Duty and Causation

Once the duty enquiry is settled, two questions remain before the court can fix liability for negligence: did the defendant fall below the standard of care that the law requires (breach), and was that failure the cause in fact and in law of the plaintiff's injury (causation). The two enquiries dovetail. The standard is fixed by reference to the reasonable man — augmented, in professional contexts, by the Bolam test — and the causation test is anchored in the but-for formula familiar from Barnett v. Chelsea & Kensington Hospital Management Committee, [1969] 1 QB 428. This chapter walks through each in turn, with the leading English authorities and the Indian applications. It picks up, in the broader Law of Torts notes, where the chapter on the duty of care and the neighbour principle leaves off, and stops short of the chapter on remoteness of damage, which deals with the outer limits of liability.

The structure of the analysis is straightforward. Breach is concerned with what the defendant did or failed to do, measured against an objective standard. Causation is concerned with whether that failure was, in the law's eyes, the cause of the harm — first as a matter of historical fact, then as a matter of legal attribution. The chapter places res ipsa loquitur in the breach analysis (it is a rule of evidence about how a breach may be proved), and treats the special problems of multi-cause and indeterminate causation through McGhee v. National Coal Board, Wilsher v. Essex AHA and Fairchild v. Glenhaven Funeral Services.

The reasonable-man standard

Breach of duty means non-observance of due care which is required in a particular situation. The standard is that of a reasonable man — an objective, impersonal benchmark that the law has cultivated through more than a century of authority. The classical formulation is in Blyth v. Birmingham Waterworks Co., (1856) 11 Ex 781:

The standard is objective. It is not what the defendant in fact contemplated, but what a reasonable man in the defendant's position ought to have contemplated. The early American case of Vaughan v. Menlove, (1837) 3 Bing NC 468, made the same point against a defendant who pleaded that he had honestly used his own best judgment in stacking a hayrick that subsequently caught fire and damaged the plaintiff's property — the law cannot be made to fluctuate with the personal capacities of each defendant.

Lord Macmillan's familiar gloss in Glasgow Corporation v. Muir, [1943] AC 448 captures the texture: the reasonable man is presumed to be free both from over-apprehension and from over-confidence. He is neither unduly timorous nor nonchalant. There is a residue of subjectivity — it is left to the judge to decide what, in the circumstances of the particular case, the reasonable man would have had in contemplation — but the standard itself is impersonal.

The factors that calibrate the standard

The standard of care is not absolute — the law does not demand the greatest possible care, only the care of a reasonable man in the relevant circumstances. Three considerations recur:

1. The magnitude of the risk. The degree of care varies directly with the foreseeable risk. A driver carrying petrol must take more care than a driver carrying water; a person carrying a loaded gun must take more care than a person carrying a stick. In Paris v. Stepney Borough Council, [1951] AC 367, the plaintiff was an employee with only one good eye, a fact known to the defendants. Goggles were not required for workmen with two good eyes, because the likelihood of injury was small; but for the plaintiff, the loss of the one good eye would mean total blindness, and the higher consequences of injury called for the higher precaution of supplying goggles. The defendants were liable.
2. The importance of the object to be attained. The law permits the assumption of some abnormal risk where the public purpose is sufficiently important. Restricting all trains to five miles an hour would prevent accidents but would slow national life intolerably. In Latimer v. A.E.C. Ltd., [1953] AC 643, an exceptionally heavy rainstorm flooded the respondent's factory; an oily film remained on the floor; the respondents spread all the available sawdust but some areas remained uncovered. An employee slipped on an uncovered patch and was injured. The House of Lords held that the risk was not so great as to justify closing down a factory employing four thousand workmen; the respondents had acted as a prudent man would, and were not liable.
3. The amount of consideration paid. The degree of care depends partly on the kind of services offered and the consideration charged. A person sipping a cup of tea at a roadside stall for a rupee may accept it as misfortune if the chair collapses; a person paying fifty rupees at a five-star hotel is entitled to a safer chair. The Delhi High Court took this further in Klaus Mittelbachert v. East India Hotels Ltd., AIR 1997 Del 201, observing that there is no difference between a five-star hotel owner and an insurer so far as the safety of the guest is concerned. The hotel charging a high price owes a high degree of care as regards the quality and safety of its structure and services. The same calibration runs through the cases on strict liability under the rule in Rylands v. Fletcher where dangerous escapes raise the standard yet further.

Special standards — children, the disabled, professionals

Where the plaintiff belongs to a vulnerable class whose presence the defendant could foresee, the standard rises. In Veeran v. Krishnamoorty, AIR 1966 Mad 282, a six-year-old boy was knocked down by a lorry while trying to cross a road on which twenty to twenty-five children were waiting to cross. The driver should have seen them from seventy-five to a hundred yards away and should have driven at a pace at which he could have stopped before reaching the place where the boys stood. Madhavan Nair, J. observed: "In the case of a child, having regard to its age, its mental development and other attendant circumstances, not much of care can be expected, and accordingly the duty of care owed to it must then be of a higher standard."

The duty owed to blind persons was explained in Haley v. London Electricity Board, [1965] AC 778. The defendants' workmen dug a trench on a London pavement and placed a long-handled hammer in front of it as a warning. The hammer-head rested across the pavement while the handle rose two feet above the ground — adequate warning for sighted persons, insufficient for the blind. There were 285 blind persons registered in the area. The plaintiff, a blind man walking carefully along the pavement on his way to work, tripped and fell into the trench. The House of Lords held that those engaged in operations on the highway pavement owe a duty to take reasonable care not to act in a way likely to endanger persons who may reasonably be expected to walk along it; that duty is owed to blind persons if the operators ought to have foreseen that blind persons may use the pavement. The duty was breached.

The standard for a person professing a special skill is the standard of an ordinary skilled person exercising that skill — the Bolam standard, taken from Bolam v. Friern Hospital Management Committee, [1957] 1 WLR 582. McNair, J. directed the jury that:

The Indian application is in Dr. Lakshman Balkrishna Joshi v. Trimbak Bapu Godbole, AIR 1969 SC 128, where the Supreme Court held that a medical practitioner must bring to his task a reasonable degree of skill and knowledge and must exercise a reasonable degree of care — "neither the very highest nor a very low degree of care and competence judged in the light of the particular circumstances of each case is what the law requires." The professional-negligence apparatus is taken further in the chapter on medical and professional negligence; the present chapter only places the Bolam standard in its breach-of-duty position.

Proof of negligence: res ipsa loquitur

The general rule is that the plaintiff bears the burden of proving negligence on the defendant's part. The maxim res ipsa loquitur — "the thing speaks for itself" — provides a recognised exception. The presumption of negligence is raised when an accident is more consistent with negligence than with any other cause, the event causing the accident was within the exclusive control of the defendant, and the facts are not known to the plaintiff but are or ought to be known to the defendant. Byrne v. Boadle, (1863) 2 H & C 722, with its barrel of flour rolling out of a warehouse window onto a passer-by, supplied the original instance, and Scott v. London & St. Katherine Docks Co., (1865) 3 H & C 596 supplied the classical formulation: "There must be reasonable evidence of negligence; but where the thing is shown to be under the management of the defendant or his servants, and the accident is such as in the ordinary course of things does not happen if those who have the management use proper care, it affords reasonable evidence, in the absence of explanation by the defendants, that the accident arose from want of care."

The Indian application is broad. In Municipal Corporation of Delhi v. Subhagwanti, AIR 1966 SC 1750, the collapse of an eighty-year-old clock tower whose normal life was forty to forty-five years told its own story; the Corporation, being in exclusive control, could not avoid the inference of negligence and was liable. In Karnataka State Road Transport Corporation v. Krishnan, AIR 1981 Kant 11, two buses brushed against each other in such a way that the left arms of two passengers in one bus were cut off below the shoulder joint; the accident itself spoke volumes about the negligence of the drivers, and in the absence of any satisfactory explanation, the defendants were liable.

Two limits should be noted. First, the doctrine is a rule of evidence, not of substantive law — it shifts the evidential burden but does not relieve the plaintiff from proving the accident itself. Second, the rule does not apply where the cause is known and a competing explanation is available; the rule operates only where the cause is unknown and the inference of negligence is the most natural one. For a cluster of cases on the operation of the maxim against state instrumentalities, see the chapter on the vicarious liability of state.

Causation in fact: the but-for test

Once breach is established, the plaintiff must prove that the breach caused the harm. The classical test of factual causation is the but-for test: the injury would not have occurred but for the defendant's breach. Barnett v. Chelsea & Kensington Hospital Management Committee, [1969] 1 QB 428 is the textbook illustration. Three night-watchmen drank tea and developed severe vomiting. They went to the casualty department of the defendant hospital. The doctor, contacted by telephone, declined to see them and advised them to go home and consult their own doctors. One of them died of arsenic poisoning some hours later. The hospital had owed the deceased a duty of care; the doctor's refusal to examine the patient was a breach of that duty. But the medical evidence was that even if the doctor had attended to the patient, the antidote could not have been administered in time to save him. The defendant's negligence was therefore not the cause of the death, and the action failed.

The but-for test is the starting point, not the whole of factual causation. Where multiple causes are sufficient to bring about the harm, or where the breach materially contributes to the injury without being its sole cause, the courts have refined the test. The cases that did the refining repay close reading.

Material-contribution causation

In McGhee v. National Coal Board, [1973] 1 WLR 1, the plaintiff worked at a brick kiln. He developed dermatitis from exposure to brick dust. The Coal Board had supplied no shower facilities; the plaintiff therefore had to cycle home covered in dust. The dermatitis was caused by abrasion of the skin by the dust. The medical evidence could not establish whether the additional period of exposure caused by the absence of showers had in fact made the difference between contracting the dermatitis and not contracting it; it could only show that the absence of showers had materially increased the risk of the disease. The House of Lords held the defendants liable. Lord Wilberforce held that where the defendant's breach materially increases the risk of the kind of harm that has occurred, the burden falls on the defendant to disprove causation.

The McGhee approach was retreated from in Wilsher v. Essex Area Health Authority, [1988] AC 1074. A premature baby received an excessive dose of oxygen due to a junior doctor's negligence and developed retrolental fibroplasia, a condition that can also be caused by four other independent agencies, each of which afflicted this baby. The House of Lords held that the plaintiff had failed to prove on the balance of probabilities that the defendant's breach was the cause: with five potential causes, it could not be said that any one of them was the cause. Mere material increase of risk was held to be insufficient where the competing causes operated through different mechanisms. McGhee was distinguished as a case where there was only one mechanism and the doctor had merely added to the dose.

The position was revisited in Fairchild v. Glenhaven Funeral Services Ltd., [2003] 1 AC 32. The plaintiffs had been exposed to asbestos by successive employers and had contracted mesothelioma. Mesothelioma is triggered by a single fibre, but the medical science could not identify which fibre or which employer's exposure had triggered the disease. The House of Lords reverted to the McGhee material-contribution-to-risk approach for the special case of a single-mechanism, indivisible disease, holding each negligent employer liable. The decision is confined to its narrow circumstances and has not been generalised.

Causation in law: the legal-cause filter

Factual causation is necessary but not sufficient. The law also asks whether the defendant's breach is a sufficient cause in law — whether the chain of causation has been broken by an intervening event (a novus actus interveniens) or by the plaintiff's own conduct, or whether the harm is too distant from the breach to be the breach's responsibility. The latter question — remoteness — is treated in its own chapter on remoteness of damage and the Wagon Mound test; the former is discussed here.

An intervening human act breaks the chain only where it is unforeseeable, voluntary and independent. In Haynes v. Harwood, [1935] 1 KB 146, the defendant's servants left a horse-van unattended in a crowded street; the throwing of stones at the horses by a child made them bolt; a policeman was injured in stopping them. The intervening act of the child was foreseeable, the policeman's intervention was a natural rescue, and the chain of causation was unbroken. By contrast, the plaintiff's own intervening act may break the chain — see the chapter on the plaintiff the wrongdoer for the cognate doctrine of ex turpi causa, and the chapter on Act of God for the parallel exception where the intervening cause is a natural force of overwhelming force.

The thin-skull rule and pre-existing conditions

The defendant takes his victim as he finds him. Where the breach causes some injury and the plaintiff's pre-existing condition causes the injury to be more serious than it would have been to a person of normal constitution, the defendant is liable for the full extent of the injury. The classical formulation is in Smith v. Leech Brain & Co. Ltd., [1962] 2 QB 405: a workman was burned by a splash of molten metal on his lip; the burn promoted a cancer to which he was already pre-disposed; he died three years later. The defendant was liable for the cancer and the death — "the test is not whether these defendants could reasonably have foreseen that a burn would cause cancer and that he would die. The question is whether these defendants could reasonably foresee the type of injury he suffered, namely the burn." The thin-skull rule operates within the breach-and-causation enquiry, not as a separate doctrine.

Damage as the gist of the action

Negligence is not actionable per se; the plaintiff must show damage. Damage means recognisable loss — physical injury, property damage, or a head of consequential loss that the law recognises. Pure mental distress short of recognised psychiatric injury is generally not actionable in a negligence frame, and the cognate doctrine on shock-induced psychiatric injury is treated in the chapter on nervous shock and recognised psychiatric injury. Pure economic loss is actionable only in a narrow class of cases, principally those falling within the Hedley Byrne framework treated in the chapter on negligent misstatement. The chapter on general, special, nominal and exemplary damages takes the analysis through to quantification; the present chapter concerns only the threshold proof of damage.

Exam angle and common pitfalls

Three pitfalls recur in objective papers. First, candidates conflate the standard of care (an objective test, what a reasonable man would do) with the existence of negligence (which requires breach and causation and damage); the reasonable-man standard is the yardstick, not the conclusion. Second, candidates treat res ipsa loquitur as a substantive ground of liability rather than a rule of evidence — the maxim shifts the evidential burden but does not impose liability where the defendant rebuts the inference. Third, candidates apply the but-for test mechanically and miss the carefully limited material-contribution-to-risk extension recognised in McGhee and confined in Wilsher: the extension applies only where there is a single mechanism and the medical science cannot identify which exposure triggered the disease. The practical sequence in any negligence problem is fixed: duty, breach, causation in fact, causation in law (which leads to remoteness), damage. Run the sequence in order, and the analysis writes itself.