Thanks for the correction, Corby.
Your point about the offence being in Scotland is interesting. I know very little about Scottish law processes but it seems they don't have offence-specific sentencing guidelines of their own. I understand (though cannot be sure) that they largely follow the E&W versions, though of course are not bound by them as courts in E&W are. That said, it seems they might be getting round to it though still have a long way to go:
https://www.scottishsentencingcouncil.org.uk/
The point I was really trying to make is that when sentencing, judges or magistrates take into account a whole raft of features. This applies to all offences from speeding to murder. There is a particular problem (in my mind) with murder as a dead victim is just as dead whatever the circumstances of his death. But the law does not see it that way and there is (whether you agree with it or not) different levels of seriousness considered when sentencing for the offence. It is not therefore appropriate (with the law as it stands) to suggest that all those convicted of murder should be incarcerated for the same amount of time.