#15667 - Causation - Tort Law

4.1 CAUSATION (CAUSE IN FACT)

Causation links actionable damage and breach of duty. It is predicated on a corrective justice model; D’s interference with the life of C resulted in loss. Causation justifies the use of negligence at all —otherwise we might as well use a social justice model.

• Honore: “to insist on a causal connection between conduct and harm ensures that in general we impose liability only on those who, by intervening in the world, have changed the course of events for the worse.”

It is based on the balance of probability, splitting the risk of error between C and D. Once D is proved as a 50%+ cause, this is treated as legal certainty (i.e. it does not make deductions in the damage recoverable because there was only a 51% likelihood that D’s act caused C’s harm) . Thus causation is invariably a question of probability, not certainty.

BUT FOR CAUSATION

The orthodox model is ‘but for’ causation —but for the actions of D, the injury that C suffered would not have occurred.

• Barnett v Chelsea Hospital [1969]: Doctor negligently told C (poisoned by arsenic) to go home. C died, but D was not liable because C would have died anyway, even if D had examined him property, but for D’s negligence, C would still have died.

Bolitho gloss: D cannot argue that his negligence was not a ‘but for’ cause because, even if he had taken the correct course of action, he would have committed another subsequent breach.

• Bolitho [1997] D (doctor) failed to respond to a call to attend to C. D argued that, even if he had attended, he would have committed a further breach (failing to intubate), so C’s harm would have occurred anyway. HL: rejected his argument. He could be held liable.

Note that D is not necessarily liable for all loss flowing from his actions if a ‘but for’ cause is established —remoteness rules still apply (see SAMMCO).

D CAUSED PART OF C’S INJURY

This can only be applied where the injury can be divided between separate factors.

• Not a part contribution to a single injury, but causing a separate injury (part of overall injury).

The test here is still ‘but for’ —need to establish, on the balance of probabilities, that injury would not have occurred but for the tort.

• Performance Cars v Abraham [1962]: C’s car was involved in two collisions. First collision damaged the underside of the car and C had been unable recover. Second collision: D damaged the front wing. QB: D only liable for the damage he had caused, not for the damage sustained in the first collision —D was not a ‘but for’ cause of the damage to the underside.

To apply Performance Cars, need to work out if the injury/damage is divisible.

• Divisible: an injury which exists on a spectrum and can get worse over time (e.g. deafness —more exposure to noise can make C deafer; if D1 exposes C for 5 years and D2 for 10 years, each will be liable for their ‘but for’ contribution —D1 1/3 and D2 2/3.)

• Indivisible: a binary injury —e.g. death / coma; everyone who has the condition is the same. If there is a mild / serious form of injury, then it is divisible and Performance Cars applies.

CONSECUTIVE / SUPERVENING INJURIES

These rules concern a contribution to a single indivisible injury. E.g. C suffers one injury from D1 (e.g. wound to a leg), but a supervening injury from D2 (e.g. loss of the same leg) occurs.

Separate and unconnected torts: where C suffers two consecutive separate tortious injuries, and D1 is before the court but D2 is not, then D1 will be liable for the damages caused by him as if the second tort had not occurred —his liability will not be reduced by the supervening harm of the second tort.

• Baker v Willoughby [1970]:C was hit by D1s car, leaving his left leg useless. D2 (a robber) shot C in the left leg, causing the leg to be amputated. C sued D1 (could not locate the robber). HL: D1 was liable to pay damages for the fact that C was unable to use his left leg for the rest of his life. D1’s argument that he should only be liable up until the time C lost his leg was rejected. D1 should not receive a windfall merely because C was unlucky in sustaining further injury.

• Lord Pearson: “The original accident… produced a general reduction of C’s capacity to do things, to earn money and to enjoy life. For that devaluation D1 should be and remain responsible to the full extent” unless before damages are assessed, something happens which “diminishes the devaluation (e.g. if there is an unexpected recovery).” If the “supervening event is a tort, D2 should be responsible for the additional devaluation caused by him.”

L+O: if D1’s argument was followed, there would be a gap in damages —D1 would pay for the injury up until the time of the subsequent tort, but D2 would only be liable for the additional damage caused (in Baker this would not have been substantial, not much difference between no leg and a useless leg). I.e. C would get no compensation for the effects of the original injury after second tort.

NB: Baker only applies where D2 is not before the court —if D2 had been before the court, Performance Cars would have applied. D would only have been liable for the injury up to the robbery, the robber would have been liable for the rest.

Second injury is not tortious: where the second injury is not tortious (e.g. a naturally occurring misfortune) then D will only be liable for the injury until it was overtaken by the supervening injury.

• Jobling v Associated Dairies [1982]: D’s negligence caused C an injury to his back. Before trial, C independently developed another back injury (not connected to the injury). HL: D was only liable for the back injury up until the time of the supervening non-tortious harm.

Reasoning is based on the ‘vicissitudes principle’: damages should not place C in a better position than she would have been in if D’s tort had not occurred. When assessing damages, the court will speculate on the effects of injury and make reductions based on the likelihood that an illness would eventually cause the same effect anyway (e.g. if injury prevents C working, but a medical condition would likely force her to stop in 10 years anyway, a reduction will be made). Where a vicissitude is known to the court before trial, there is no need to speculate —the court can make an exact deduction.

The vicissitudes principle only applies to innocent/non-tortious hypothetical or actual subsequent harms, hence the distinction between Jobling and Baker.¹

PART CAUSING A SINGLE INJURY

While Performance Cars is about causing part of a divisible injury, this is about a contribution to a single, indivisible injury.

If an injury is necessarily indivisible and causes cannot be divided between spate factors because those factors operate cumulatively and interdependently, then apply Bonnington:

• Bonnington Castings v Wardlaw [1956]: employee was exposed to silicon dust from two sources, but only one source was attributable to D’s negligence. C developed a lung condition that gradually developed over time. Lord Keith: exposure to ‘innocent’ and ‘guilty’ sources were simultaneous, so could not be divided into chronological chunks. The condition wouldn’t have happened (or wouldn’t have occurred when it did) ‘but for’ the exposure to guilty dust, so D was liable for C’s injury.

Lord Phillips in Sienkiewicz on the difference between Bonnington and Performance Cars: “Where the disease is indivisible, such as lung cancer, D who has tortiously contributed to the cause of the disease will be liable in full. Where the disease is divisible, such as asbestosis, the tortfeasor will be liable in respect of the share of the disease for which he is responsible.”

There is a question as to whether Bonnington is an orthodox application of causation principles. Green argues that it is, just used where there is a difficult factual situation —i.e. in Bonnington, D is a ‘but for’ cause because without D the injury wouldn’t have occurred (or wouldn’t have occurred when it did). This was the approach taken by the Privy Council in Williams.

Williams v Bermuda Hospitals Board [2016]

• Facts: C was admitted to hospital with appendicitis. The hospital was negligent in failing to diagnose the appendicitis and took more than 10hrs to operate. As a result, pus leaking from the appendix caused sepsis to set in and injury to C’s heart and lungs. Issue: some of the leakage was non-negligent (would have occurred anyway) and some was the result of the hospital’s negligence (in not operating fast enough).

• Lord Toulson (PC): C’s injuries were indivisible (not greater / smaller depending on the amount of leakage). As such, Bonnington applied: “where D has been found to have caused or contributed to an indivisible injury, she will be held fully liable for it, even though there may well have been other contributing causes.” The hospital was liable for the full injury.

McBride:

• Different rule: Lord Toulson followed Sarah Green’s approach that Bonnington is a straightforward application of ‘but for causation’. However, McBride disagrees —it is a different rule because it does not ask if D’s conduct is a but for cause, it asks ‘did D’s negligence make a material contribution to the state of affairs that resulted in C suffering an indivisible injury’?

• Bonnington not solid authority: the PC note pneumoconiosis is a divisible disease, so Bonnington may just be a Performance Cars case where the HL went wrong in holding D liable for the whole injury, rather than just a part (i.e. he was a part cause on straightforward ‘but for’ causation). It may not be solid authority for a subversive rule now embedded in...