Factual Causation and Remoteness in Tort

Factual causation asks whether the defendant’s breach actually caused the claimant’s harm. Legal causation, in the sense of remoteness, asks whether that harm is sufficiently connected to the breach for the defendant to be liable. In a negligence problem, answer these as two separate questions.

Factual causation: the “but for” test

Ask: But for the defendant’s breach, would the claimant have suffered the harm? If the harm would have happened anyway, the breach is not a factual cause.

For example, a driver carelessly hits a pedestrian, who breaks an arm. If the pedestrian would not have broken their arm but for the collision, factual causation is established. By contrast, in Barnett v Chelsea & Kensington Hospital, the hospital’s failure to examine a patient did not cause his death: he would have died from arsenic poisoning even with proper treatment.

Legal causation: remoteness

A defendant is not liable for every consequence that follows a breach. Under the remoteness test in The Wagon Mound (No 1), the type of damage must have been reasonably foreseeable when the breach occurred. The precise way the damage happened does not have to be predicted.

In the driver example, a broken arm is a foreseeable type of physical injury from hitting a pedestrian, so it is not too remote. If a claimant has an unusual vulnerability that makes the injury much worse, the defendant generally takes the claimant as they find them. This is known as the thin skull rule; it concerns the extent of a foreseeable type of injury.

Exam mistake to avoid: do not use “but for” to decide remoteness. First decide whether the breach made a difference to what happened; then decide whether the type of harm was reasonably foreseeable.