One thing that leaps out at me from the report is that he was sentenced, not for murder, but for manslaughter. Traditionally, both are unlawful killings but there are vast differences between the two.
Murder, traditionally (and I'm basing this on Australian law which was derived from the UK) involves one major element that maslaughter does not: intent. This is why there can be a huge discrepancy between sentences for murder and sentences for manslaughter.
In Queensland, the jurisdicition I work in, murder involves an intention either to kill or to do grievous bodily harm. Manslaughter is the killing of a person without lawful excuse but without the requisite intention.
Murder will get you life - that's a mandatory sentence. Manslaughter can get you life, but it's not mandatory and can be mitigated by other factors, such as the actual facts surrounding the killing and the personal circumstances of the offender. People convicted of manslaughter can even avoid being sent to gaol at all.
Without knowing all the facts that the court knew when sentencing the offender, I think it's a bit presumptuous to question the sentence imposed.
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Jim_in_Oz
If you're going to jump across a well, try to do it in one jump or less.