er I would do a quality check on this zarzee
here is a useful link
http://sixthformlaw.info/01_modules/mod3a/3_30_murder/03_murder_mens.htm
The mens rea has definitely changed for murder has changed over the last fifty years ( in this country UK ). It USED to be - killing ( act linked with an intention to do the slightest harm, and could even be linked with an intention to do something else ( burglary, rape I think - it was all such a long time ago ) This was a category called constructive murder
In the list I have given you above there should be the case lurking where the Lord Chief Justice says - " the sooner we get to murder-you mean to do it and manslaughter you dont - the better ". This can be taken as the LCJ determined to kill the offences of constructive murder and constructive manslaughter - or at least consign them to a grave. I do not know how far he has been successful - which is the content of your question.
PS I think the mens rea for murder is intention to do GBH - ie lower than to kill but I am not sure. see above
voluntary manlaughter o god my brain hurts
all this was terribly terribly important fifty years ago as you hanged murderers ( they swung ! ) and imprisoned those guilty of manslaughter