FLK2 · Criminal Liability

Causation in crime

SQE1 revision notes — the key rules, leading cases and common traps for this topic, in plain English and current to 2026.

CRL.02 — Causation in Crime

For any result crime (e.g. murder, manslaughter, s.18/s.20 OAPA 1861, criminal damage), the prosecution must prove the defendant's conduct caused the prohibited result. Causation splits into factual and legal causation; both must be satisfied.

Factual causation — the "but for" test

But for D's conduct, would the result have occurred? If it would have happened anyway, factual causation fails. R v White [1910] (son poisoned mother's drink; she died of an unrelated heart attack first — no factual cause; convicted only of attempt). This is a necessary minimum, not enough on its own.

Legal causation — D's act must be a substantial and operating cause

More than minimal/de minimis: the contribution must be substantial (not trivial) — R v Hughes [2013] clarifies it need not be the sole or main cause, but must be more than negligible.
Operating cause: D's act must still be operating at the time of death — R v Smith [1959] (stab wound still the operating and substantial cause despite poor medical treatment).

The thin-skull rule

Take your victim as you find them — physical, psychological, and religious/belief characteristics. R v Blaue [1975] (Jehovah's Witness refused a blood transfusion; refusal did not break the chain).

Intervening acts (novus actus interveniens) — chain-breakers

Medical treatment: rarely breaks the chain. Only if treatment is "so independent of D's acts and so potent in causing death" that the original wound is merely the setting — R v Cheshire [1991]; contrast R v Jordan [1956] ("palpably wrong" treatment, wound healed).
Victim's own act: breaks the chain only if free, deliberate and informed, or if D's escape-prompting conduct made the victim's reaction not "daft"/disproportionate — R v Roberts [1971]; R v Williams & Davis [1992].
Drug supply: the victim's free, voluntary self-injection breaks the chain — R v Kennedy (No 2) [2007].
Third party acts: break the chain only if free, deliberate and informed and not foreseeable.

Common traps

"But for" alone is never sufficient — always go on to legal causation.
Bad medical treatment almost never breaks the chain (Cheshire is the rule, Jordan the rare exception).
D need not be the only cause; substantial-and-operating suffices.
Thin-skull covers beliefs, not just physical frailty (Blaue).
Self-injection (Kennedy) breaks the chain; mere supply does not cause death.

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A woman is the treasurer of a small amateur football club. Members pay £20 each month in cash. Under the club rules she accepted on becoming treasurer, she must bank the subscriptions into the club's dedicated account within seven days. One month she receives £200 in subscriptions and spends the cash on her own gas bill that same day. She intends to replace the money from her wages before anyone notices, and pays an equivalent £200 into the club account two weeks later. Which statement best explains how section 5(3) of the Theft Act 1968 applies to the subscriptions when she pays the gas bill?

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