For murder, a person must commit an unlawful killing, being one which cannot be excused or justified in law. This means that unless a person can point to a defence which makes the killing lawful, their actions are unlawful.
For example, the law will justify a killing from an act of self-defence which was proportionate in the circumstances. By contrast, the law will not justify a killing where the force used was excessive. In these circumstances, the law will treat this as an unlawful killing which can be tried as a murder.
The majority of cases in this area have dealt with two issues:
1 – Whether the actions of law enforcement authorities, such as the police and military, are no longer justified due to an excessive use of force.
2 – Whether medical professionals are entitled to remove life-sustaining treatment, such as artificial feeding and ventilation, from their patients, without this amounting to an unlawful killing.
Each of these areas will be explored in the cases below:
Excessive use of force
The first case considers circumstances where law enforcement authorities use excessive force, and consider whether this constitutes an unlawful killing.
R v Clegg 
A killing by a soldier on active service or a police officer during the course of their duty, will usually not be unlawful. This is due to the plea of self-defence. However, where the force used is excessive the killing can amount to murder.
Acts by medical professionals
The following cases considered what acts or omissions by a medical professional, if any, constitute an unlawful killing. The Courts have draws a robust line between the removal of life-sustaining treatment, which is lawful, and actively bringing about a patient’s death, which remains unlawful as a form of euthanasia.
Airedale NHS Trust v Bland 
It is not an unlawful killing where medical professionals remove life-sustaining treatment in circumstances where the continuation of the treatment is not in the best interests of the patient.
R v Cox 
In R v Cox, medical professionals were held to have unlawfully killed their patient because they did a positive act to bring about their death. Airedale NHS Trust v Bland was distinguished as the medical professionals were asking to omit to care for their patient.
Re A (conjoined twins) 
There is a difference between medical treatment which has the primary purpose of killing a patient – which is unlawful – and medical treatment which has the incidental consequence of killing a patient – which is lawful.