[QUOTE 3941631, member: 9609"]to me there is a significant difference between the two incidents, if you go out on the rob and steal a vehicle then you have had time to weigh up the various scenarios and possibilities, someone being killed is a very realistic outcome, and for me this comes very close to full murder. If someone of otherwise good character going about their lawful business in a moments madness commits an act of rage and someone dies, then for me this is quite along way from being full murder (could well deserve a life sentence, but it is a long way off premeditated murder)[/QUOTE]
Murder is a common law offence. As such it has no statutory definition. However, legal arguments around the necessary points to prove are encapsulated in case law, and any doubts or defences etc can be explored that way.
The archaic term "Malice Aforethought" is the definition of intent we need to consider. How and when that malice is formulated is immaterial, and does not require the prosecution to prove a timescale as such. The phrase may suggest a lengthy or drawn out period of preparation based on a plan to kill somebody, but that malice can actually be decided on instantly. Your phrase "moment of madness" sums it up, (although of course that "madness" is not to be confused with mental health as it would make it mitigation or even a defence). That moment when the person in a fit of rage thinks "I'm going to kill him" and then drives three tonnes of car at him intending at that time that the consequence of that action will be to kill him is sufficient "aforethought".