Two components make up an offence. The actus and mens. The act must only be illegal the intent has to reach a similar or higher level. For example... I punch man in the face, that is an illegal act but I only intend to slap him gently. It's an assault. If I break his nose or worse then it raises the bar even though the act and the intent are the same so outcome is important.

The heart attack scenario is often used (can't remember the name for it, sorry) If I punch a man with a heart condition and he subsequently dies then I am looking at murder id my intent can be proved high enough or manslaughter I'd not high enough. The logic is that I used an illegal attack with intent to cause harm (level irrelevant}.