4.3 Doctrine of Causation

The result-crimes' bridge: the act must have CAUSED the prohibited result. The two levels: Factual causation (the conditio sine qua non): the "but-for" test — but for the act, would the result have occurred when it did? The necessary condition; insufficient alone (the thousand "but-for" causes — the mother's giving birth to the murderer problem); Legal causation (the proximate/imputing cause): among the necessary conditions, which does the law PUNISH? The tests: the operating-and-substantial-cause approach (was the accused's act an operating and substantial cause of the result?). The doctrines of the intervening acts: (i) novus actus interveniens — a fresh intervening act (a third party's deliberate wronging, a victim's wholly abnormal response) breaking the chain; (ii) the thin- skull rule — take the victim as found: the blow that kills the haemophiliac is homicide nonetheless ("you take your victim as you find him" — the eggshell-skull rule); (iii) the medical- treatment problem (negligent treatment rarely breaks the chain — the wound remains the operating cause; only GROSSLY negligent independent treatment severs); (iv) the accelerating- cause cases (the act that hastens an inevitable death still causes it).