bits of law

Main Section

Criminal | Offences Against The Person

Murder: Actus Reus

Study Note | A Level

Download Adobe PDF Icon


Homicide is the killing of a human being by another and murder is an example of unlawful homicide. Other unlawful homicides include manslaughter, both involuntary and voluntary.

Murder is a common law offence which has not been defined by statute. Sir Edward Coke’s seventeenth century definition: ... the unlawful killing of a reasonable person in being and under the King’s peace with malice aforethought, express or implied.. is widely referenced. The actus reus is described by the first part and mens rea by the second.

The actus reus of murder requires three elements to be satisfied: unlawful killing, a reasonable person in being and under the King’s peace.

Unlawful Killing

Some killing may be justified in law such as killings resulting from self defence or in the prevention of crime, so long as reasonable force has been exercised. Also some killings may be authorised, for example during wartime or judicial executions.


Killing may be the result of an omission. The actus reus of murder may be present if a person has a duty to act, fails to do so and a death occurs. Duties may be imposed in a variety of ways.

  • Contractual duty

    Pittwood (1902)

    Defendant was a railway crossing keeper and omitted to shut the gate. A person crossing the track was hit and killed by a train. The duty to close the gate was imposed on the defendant through his contract. Defendant was guilty of manslaughter.

  • Duty from special relationship

    Gibbins and Proctor (1918)

    Defendants, a father and his mistress, failed to feed a child and the child died of starvation. Defendants were guilty of murder.

  • Duty taken on voluntarily

    Stone and Dobinson (1977)

    Defendants allowed Stone’s sister to live with them. She became ill and unable to care for herself and died. Defendants had assumed some responsibility and so had a duty of care towards the sister. Defendants were convicted of manslaughter through failing to care for her or summon help when she became helpless.

  • Duty arising from setting in motion a chain of events

    Miller (1983)

    Defendant, a squatter, accidentally set a mattress alight. When he realised he left the room and went to sleep in another. He did not attempt to put out the fire or summon help. Defendant found guilty of criminal damage because once he realised what had happened he had a duty to minimise the damage.

    Khan [1998]

    Defendant supplied a girl with heroin. She accidentally overdosed and the defendant left her to die. It was found the actus reus of the offence was the omission to summon medical assistance and not the supply of heroin.

A Reasonable Person in Being

This element alludes to difficult questions about the meaning of existence and how we categorise life in the application of the law. Such issues are raised in cases involving the status of a foetus or someone on a life support machine.

  • Foetus

    Attorney General’s Reference (No. 3 of 1994) (1997)

    A foetus in the womb, is deemed to have no existence independent of its mother so is not defined in the law as a reasonable person in being. However, if the foetus is deliberately injured and after being born the child dies from the injuries then the attacker would be criminally liable. Manslaughter would be the likely charge.

  • Life Support Machine

    Doctors are allowed to switch of life support machines of patients who are deemed brain dead without being liable for unlawful homicide. Therefore it can be implied that someone considered to be brain dead is not a reasonable person in being although no cases explicitly say this.

    Malcherek (1981)

    Defendant attacked the victim, causing severe injuries which required the victim to be placed on a life support machine. Doctors decided to switch the machine off as there was no prospect of recovery and soon after the victim died. It was held the operating and substantial cause of death was the original wounds and defendant was found guilty of murder.

Under the King’s Peace

This relates to the exemption for the killing of an enemy during war, as such a person is not under the King’s peace. However, the actus reus of murder would apply to the killing of a prisoner of war.

Jurisdiction for Prosecution

A British citizen can be tried in the domestic courts for a murder alleged to have been committed in any country. A prosecution may be brought anytime after the death. However, if the death occurs over three years after the injuries which caused it then the Attorney General’s permission must be gained. This also applies if a person has already been found guilty of an offence connected to the circumstances of the death.


Actus reus of a crime is the defendant’s guilty act. For many crimes the act must have caused a particular consequence. In order to determine if the defendant’s guilty act caused the required consequence the rules of causation must be applied. For example, in relation to offences against the person, the defendant’s act must have caused the injury to the victim which is relevant for the particular offence. If there is no causation, the act is not unlawful or there is no criminal liability.

Factual causation

The defendant can only be found guilty if the consequence would not have happened but for the defendant’s conduct.

White (1910)

Defendant put cyanide in his mother’s drink intending to kill her. His mother died of a heart attack before the poison could take effect. So defendant had intended to kill his mother and she had died. However, his were not the cause of her death. So defendant found not guilty of murder although he was guilty of attempted murder.

Pagett (1983)

Defendant was shooting at police and used his pregnant girlfriend as a human shield. The police fired back and the girlfriend was killed. Defendant was convicted of her manslaughter. Victim would not have died but for defendant’s actions.

If the prohibited result would have occurred, even without the defendant’s actions, then something other than the defendant’s conduct caused it and the factual causation is not present.

Legal causation

In addition to factual causation, legal causation must also be proved. Criminal liability is defined by the link between the act and the consequence, known as the chain of causation, which must be unbroken.

  • Substantial to minimal cause

    The cause of death in unlawful killing can vary, from substantial to minimal. The law requires the conduct to be more than a minimal cause of the death but it does not need to be a substantial cause. Defendants may be found guilty of unlawful homicide if their actions contributed to the death or if he was one of many who contributed to the death.

    Cato (1976)

    Defendant was a drug addict and spent the night with a friend injecting each other with a mixture of heroin and water. In the morning both felt ill and the victim died. Court of Appeal found that the heroin need not be the only cause of death, but that it was more than a minimal cause which accelerated the victim’s death.

  • ‘Thin skull rule’

    The general principle is that the defendant must take the victim as he finds them, so the law does not take into account any particular characteristics of the victim. If the victim has something unusual about them which makes the injury more serious the defendant is still liable for the resulting injury.

    Blaue (1975)

    Defendant stabbed a woman and punctured her lung. The victim refused a blood transfusion as it was contrary to her religious beliefs and died the next day. The principle that a defendant must take their victim as they find them was found to apply to the mental as well as the physical characteristics of the victim. It was held the stab wound caused the victim’s death.

  • ‘Novus actus interveniens’

    Sole cause of injury or death is an independent act.

    Malcherek (1981)

    Defendant attacked the victim, causing severe injuries which required the victim to be placed on a life support machine. Doctors decided to switch the machine off as there was no prospect of recovery and half an hour later the victim died. Defendant was convicted of murder and appealed on the grounds that the doctor’s intervention had broken the chain of causation. It was held the operating and substantial cause of death was the original wounds. The effect of the life support machine had been merely to hold the effect of the injuries in suspension, once the machine was turned off it was the effect of the original wounds which caused the victim’s death. Therefore there was no break in the chain of causation.

    In medical intervention cases, doctors will only be considered to have caused the injury or death if treatment is seriously wrong.

    Jordan (1956)

    Defendant stabbed the victim, who was taken to hospital. A week later, the wound had nearly healed. Doctors injected antibiotics in error, the victim had a severe allergic reaction and died. The administration of medical treatment had been palpably wrong. Defendant’s original action was not the operating and substantial cause of death. Defendant guilty of wounding but did not cause the death of the victim.

    Smith (1959)

    Defendant, a soldier, had a fight with another soldier and stabbed him in the lung. The victim was carried to a medical centre by others but he was dropped twice on the way. At the medical centre, the victim was given artificial respiration by chest compressions. An hour later the victim died. Defendant argued chain of causation had been broken by errors made in an attempt to care for the victim. Court held the defendant’s stabbing was the operating and substantial cause of the victim’s death. Defendant convicted of murder.

    Cheshire (1991)

    Defendant shot the victim in thigh and stomach. Victim had trouble breathing and was given a tracheotomy. Victim died of rare complications from the tracheotomy which had not been spotted by the doctors. Despite the fact the gunshot wounds were no longer life threatening, the tracheotomy and the rare complications were not seen as independent of the original act and so the chain of causation was not broken.

  • Victim’s own act

    If the defendant causes the victim to act in a foreseeable way then the victim’s own act will not break the chain of causation. This depends on whether the victim’s conduct is reasonable or unreasonable.

    Roberts (1971)

    Victim jumped from a car in order to escape from defendant's sexual advances. The car was travelling between 20-40mph. Victim was injured from jumping out of the car. Defendant was found liable for the injuries.

    Williams (1992)

    Defendant gave a lift to hitch hiker, the victim, and allegedly tried to rob him. Victim jumped from the car and died from head injuries. Court of Appeal asked whether the victim’s conduct was: .. within the ambit of reasonableness and not so daft as to make his own voluntary act one which amounted to a novus actus interveniens and consequently broke the chain of causation....

This site is best viewed with style sheets (CSS) enabled and an up-to-date browser.