Introduction
In criminal law, establishing a clear and unbroken chain of causation between the defendant’s act and the prohibited consequence is fundamental to proving guilt. This issue becomes particularly complex in cases involving homicide where the victim dies after voluntarily consuming drugs supplied by the defendant. The principle provided, drawn from the leading House of Lords decision in R v Kennedy (No 2), establishes a clear line of responsibility in such scenarios. It holds that the free and informed decision of an adult to self-administer a dangerous drug constitutes a novus actus interveniens (a new intervening act), which breaks the chain of causation from the supplier. This note will explain the legal reasoning underpinning this principle, focusing on its application within the framework of unlawful act manslaughter and the Offences Against the Person Act 1861.
The Problem of Causation in Unlawful Act Manslaughter
For a defendant to be liable for unlawful act manslaughter, the prosecution must prove three elements: (1) the defendant committed an unlawful act; (2) the act was objectively dangerous; and (3) the act caused the victim’s death (Herring, 2022). In cases like the one involving Deacon and Osei, the unlawful act is typically the supply of a controlled drug. The supply of heroin, a Class A drug, is undoubtedly dangerous. The central legal difficulty, however, lies in proving the third element: causation.
Causation requires proof of both factual and legal causation. Factual causation is established using the 'but for' test: but for the defendant’s act, would the result have occurred? In our scenario, but for Deacon supplying the heroin, Osei would not have died. Factual causation is therefore satisfied. Legal causation, however, is more complex. It asks whether the defendant’s act was a ‘substantial and operating’ cause of the death (Smith, 1959). This chain of legal causation can be broken by an intervening act that is sufficiently independent of the defendant's original act.
The Principle of a Free, Deliberate and Informed Act
The law generally holds that a free, deliberate, and informed act of a responsible adult will break the chain of causation. As stated by Professor Hart and Honoré, this principle respects individual autonomy and responsibility (Hart and Honoré, 1985). The House of Lords in R v Kennedy (No 2) [2007] UKHL 38 authoritatively applied this principle to drug supply cases, clarifying years of conflicting decisions from the Court of Appeal, such as in R v Dias [2002] 2 Cr App R 5. The facts of Kennedy (No 2) are analogous to those concerning Deacon and Osei: the defendant prepared a syringe of heroin and gave it to the victim, who then chose to self-inject and subsequently died from an overdose.
The House of Lords unanimously held that the defendant was not guilty of manslaughter. Their reasoning rested on two key points. First, they considered the potential unlawful act of administering a noxious thing under section 23 of the Offences Against the Person Act 1861. The court determined that "administering" a substance requires an application of the substance to another person. Because the victim, a "fully informed and responsible adult," self-injected, the defendant did not administer the drug. The victim administered it to himself.
Second, and more fundamentally, the court found that the victim's act of self-injection was a novus actus interveniens. Lord Bingham stated that "the criminal law generally assumes the existence of free will." He concluded that the defendant "is not to be treated as causing V to act in a certain way if V makes a voluntary and informed decision to act in that way rather than another" (R v Kennedy (No 2), at [14]). In the scenario provided, Osei was an adult who understood he was taking heroin. His decision to inject the drug was his own. Deacon’s role was to facilitate Osei's act, not to cause it. The final, fatal act was performed solely by Osei, breaking the chain of causation that linked Deacon to his death.
Conclusion
The principle derived from R v Kennedy (No 2) provides a clear and certain rule in a difficult area of law. A defendant who supplies drugs to a fully informed adult, even where they prepare the syringe, will not be liable for manslaughter if that adult voluntarily self-administers the drug and dies. The law identifies the victim’s own free act as the legal cause of their death. Applying this to the facts, Deacon’s actions in preparing and handing the syringe to Osei are insufficient to establish legal causation for the death. His conduct amounted to facilitation, but the law places responsibility for the fatal administration on Osei, whose free, deliberate, and informed act broke the chain of causation. While the defendant remains liable for the separate offence of supplying a controlled drug, they cannot be held criminally responsible for a death that was, in the eyes of the law, caused by the victim's own autonomous choice.
References
- Hart, H.L.A. and Honoré, T. (1985) Causation in the Law. 2nd edn. Oxford University Press.
- Herring, J. (2022) Criminal Law: Text, Cases, and Materials. 10th edn. Oxford University Press.
- Offences Against the Person Act 1861 (c. 100).
- R v Dias [2002] 2 Cr App R 5.
- R v Kennedy (No 2) [2007] UKHL 38.
- R v Smith [1959] 2 QB 35.
