Causation Notes

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...

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