Murder is a common law offence, meaning that it is not set out in an Act of Parliament.
Lord Coke gave the classic definition of murder, which was updated to be: "the unlawful killing of a reasonable creature with malice aforethought."
AR - the unlawful killing of a reasonable creature
The unlawful act can be done through an act or an omission.
A killing will be unlawful when there is no justification - examples of justified killings would be those done in self defence (consider the case of Tony Martin), through police duties, through necessity or through the withdrawal of medical treatment.
A victim is considered to be a reasonable creature if they are independent of their mother (in regards to a foetus), as ruled in the case of AG Ref. No3. In terms of critically ill people, it must be considered whether the brain stem has died - R vs. Malcherek and Steel.
(Consider the laws on causation for the AR - is there a clear link between the defendant's actions and the consequence (i.e. the death)?)
Express malice aforethought is the intention to kill.
Implied malice aforethought is the intention to cause GBH/serious harm.
R vs. Vickers told us that a defendant doesn't need to intend to kill in order to be guilty of murder - the intention to cause GBH will suffice. R vs. Cunningham approved this decision.
Direct and indirect intention is applied to both levels of the MR.
Direct intention will consider whether it was the D's aim/purpose (R vs. Mohan) to kill/cause GBH.
Indirect intention will consider whether the killing/GBH was a "virtual certainty" (R vs. Woollin) given the D's actions and whether the D was aware of this.
If a D is found guilty of murder, then the judge must impose a mandatory life sentence.