The time served will be ten years for one offender, eight for the other two, hardly seems commensurate with the crime does it?
How are you measuring what is commensurate? Bear in mind they were (frustratingly but probably correctly) convicted of manslaughter -accidental killing - not murder. If 'commensurate' means to you that they should suffer the same fate as the victim, then I've got a problem with that. Come back and tell me this is the right thing if/when someone in your family accidentally runs a red light and kills someone.
But it will be defended as we all live in a "civilised society"! well some of us do, others don't and civilised punishments don't work on these people, they need uncivilised punishments and a life sentence with a min term served of 25 years would soon wipe the smirk of their grinning faces.
Where do you live? I live in the UK, which has something like the tenth-lowest murder rate in the world (i'm excluding micro-nations like the Vatican and Tuvalu here). I grew up on a pretty rough council estate where there was (relative speaking) plenty of crime but most people were still decent and law-abiding, and we had policing with consent. If we administer, by your own admission, 'uncivilised' punishments, then we are as bad as the criminals, and trust in the law breaks down. There's little evidence that that excessive sentencing functions as much of a deterrent.
Or is the dig at 'uncivilised society' a dig at travelling communities? I hope not because that would display prejudice and racism.
Anyone who thinks 10 years is a suitable punishment should ask themselves "what will he do when he comes out?" Perhaps become a counsellor ? or work in adult social care? OR go back to to being a thieving piece of scum only getting his 25 years when he inevitably murders some other poor victim?
Again they've not been convicted of murder. It's important that we provide education when people are in prison and take steps to find them useful employment when they come out. We don't know what these guys are likely to be like when they come out but for most of us our 30-year-old selves are very different from our teenage years , and given suitable support there's every prospect they will live fruitful lives. This has to be better than giving teenagers whole life sentences for manslaughter based on what they might do in the future?
We don't live in Scandinavia, don't have a criminal system based on rehabilitation and we won't be getting that anytime soon, so we have to lock these people away, if only to protect ourselves.
Our criminal justice system is meant to be rehabilitative. Others' systems work much better than ours. If you're going to call for change, wouldn't it be better to call for (i) better and more humane prison services with more scope for learning and living a worthwhile life on release than (ii) more whole-life sentences, including for manslaughter? The first has to be the better option and frankly is the more likely to happen as no developed society has anything like (ii). You know this is the right answer, don't you? Or are you more interested in revenge than justice?