This is decided using the “but for” test:

But for the defendant’s conduct, would the result have happened anyway?

If the answer is “yes,” the defendant is not the factual cause.

• R v White [1910] – The defendant poisoned his mother’s drink, but she died of a heart attack before the poison worked. His act was not the factual cause of death.

• R v Pagett [1983] – The defendant used his girlfriend as a human shield while shooting at police. They returned fire and killed her. “But for” his actions, she would not have died, so factual causation was proven.

Even if factual causation exists, the law only holds the defendant liable if their conduct was a substantial and operating cause of the result. The chain of causation must remain unbroken.

• R v Kimsey [1996] – The defendant’s driving need only be “more than a slight or trifling link” to the death.

• R v Hughes [2013] – There must be some element of fault; mere presence at the scene is not enough.

The link between conduct and result can be broken by a new, independent event. There are three main types:

(a) Acts of the Victim

If the victim reacts in a way that is reasonably foreseeable, the chain remains intact.

• R v Roberts [1971] – A woman jumped from a moving car to escape sexual advances. The defendant was still liable as her reaction was foreseeable.

• R v Williams and Davis [1992] – The chain was broken where the victim’s reaction was so unreasonable it could not have been predicted.

(b) Acts of Third Parties

A third party’s act breaks the chain only if it is so independent and potent that it makes the defendant’s contribution insignificant.

• R v Cheshire [1991] – Poor medical treatment did not break the chain because the original injury was still a significant cause.

• R v Jordan [1956] – The chain was broken where doctors gave treatment that was “palpably wrong” and the original wound had almost healed.

(c) Natural Events

An unpredictable and extraordinary natural event can also break the chain, though this is rare in modern cases.

The defendant must “take the victim as they find them.” If the victim has a weakness or condition that makes the result more serious, the defendant is still fully liable.

• R v Blaue [1975] – The victim refused a blood transfusion for religious reasons and died. The defendant was still responsible for her death.