The case law on involuntary manslaughter is voluminous; the cases below represent the doctrinal landmarks most frequently encountered in tutorials and examinations.
On unlawful act manslaughter, R v Church [1966] 1 QB 59 is foundational. Edmund Davies J articulated the requirement that the unlawful act be 'dangerous' in the objective sense—conduct that 'all sober and reasonable people would inevitably recognise must subject the other person to, at least, the risk of some harm.' The judgment firmly rejected purely subjective approaches and emphasised that constructive liability is tempered by an objective threshold of dangerousness.
R v Dawson (1985) 81 Cr App R 150 clarified that 'harm' means physical harm. The defendants attempted to rob a petrol station; the attendant, who had a serious heart condition unknown to the defendants, suffered a fatal heart attack. The Court of Appeal quashed the conviction: emotional shock or fear, absent physical injury, does not satisfy the dangerousness requirement. By contrast, R v Watson [1989] 1 WLR 684 held that if the defendant becomes aware during the course of the unlawful act that the victim is frail or vulnerable, that knowledge is imputed to the reasonable observer for the purpose of assessing dangerousness. In Watson, the defendants burgled the home of an 87-year-old man who died of a heart attack 90 minutes later. The Court of Appeal held that the jury was entitled to find the act dangerous once the burglars realised the victim's age and frailty, although on the facts the causation link could not be proved and the conviction was quashed.
R v Kennedy (No 2) [2007] UKHL 38 established that a competent adult's free, informed, voluntary act breaks the chain of causation. The defendant prepared a syringe of heroin and gave it to the victim, who self-injected and died. The House of Lords held that the victim's own act of injection was the immediate cause of death; the defendant's supply and preparation were not sufficient to constitute the actus reus of manslaughter. Lord Bingham emphasised the importance of personal autonomy: a person of full age and capacity who voluntarily administers a noxious substance to himself does so as a free agent, and causation cannot be attributed to another. Kennedy has been widely applied in subsequent 'drug supply' cases and represents a significant restriction on the boundaries of unlawful act manslaughter.
On gross negligence manslaughter, R v Bateman (1925) 19 Cr App R 8 was the leading authority for seventy years. Lord Hewart CJ held that negligence must go 'beyond a mere matter of compensation' and show 'such disregard for the life and safety of others as to amount to a crime against the State.' The formulation was picked up and refined in Andrews v DPP [1937] AC 576, where the House of Lords approved the Bateman test in the context of a road traffic fatality.
R v Adomako [1995] 1 AC 171 re-stated the test in language drawn directly from the law of tort. The defendant was an anaesthetist who failed to notice that an oxygen tube had become disconnected during surgery; the patient suffered a cardiac arrest and died. The House of Lords held that the jury must find: (i) a duty of care; (ii) breach; (iii) causation; and (iv) that the breach was so gross as to be criminal. Lord Mackay LC emphasised that the jury makes the final moral evaluation of whether the conduct was 'so bad' as to warrant a criminal conviction. Adomako has been criticised for circularity—defining a crime by reference to whether it is 'criminal'—but it remains the authoritative statement.
R v Misra [2004] EWCA Crim 2375 confirmed that the relevant risk is one of death, not merely serious injury. The Court of Appeal rejected a challenge under Article 7 ECHR (legal certainty), holding that the test in Adomako is sufficiently certain for a jury properly directed. The decision reasserted the centrality of the jury's evaluative judgment and dismissed arguments that gross negligence manslaughter is unconstitutionally vague.
R v Rose [2017] EWCA Crim 1168 (Court of Appeal) provided detailed guidance on directing juries, endorsing a model direction that requires the jury to find an 'obvious and serious risk of death' and to assess whether the breach was 'truly exceptionally bad.' While not altering the Adomako framework, Rose emphasises clarity in jury directions and signals judicial concern about inconsistent application.