BEDNOBS, on the CPS website it says,
"Gross Negligence Manslaughter
This is where the death is a result of a grossly negligent (though otherwise lawful) act or omission on the part of the defendant. The law in respect of this has been clarified in the case of R v Adomako (1994) 3 All ER 79 where a four stage test for gross negligence manslaughter known as the Adomako Test was outlined by the House of Lords:
The test involves the following stages:
a) the existence of a duty of care to the deceased;
b) a breach of that duty of care which;
c) causes (or significantly contributes) to the death of the victim; and
d) the breach should be characterised as gross negligence, and therefore a crime."