Purpose of the courts is not retribution
It seems to me that the essential ingredients of murder - malice and an absence of some provocation - were missing. This lesser charge would have been pleaded to and a lot of trauma and harrowing detail could have been spared on the families of all concerned.
In any event, a jury found the accused guilty of manslaughter. The judge got it about right when he passed a sentence of four years on the guilty party. We must respect what can and cannot be put before a court and obey decisions of the DPP, the judge and prosecution.