Whatever view is taken about the length of minimum sentence passed on Ian Huntley, Mr Justice Moses has performed a valuable service in explaining how he arrived at the term of 40 years.
The families of Ian Huntley's victims arrive at the High Court
It demystifies the process of judicial decision-making in one of the most sensitive areas of criminal law.
It also demonstrates that, despite hearing from the victims' families, the judge stuck closely to the sentencing formula incorporated in the Criminal Justice Act 2003 which ended the Home Secretary's role in setting the tariffs of murderers.
Two of the factors in a murder which would trigger a "whole-life" tariff are premeditation and sexual conduct. Neither was proved in Huntley's trial.
Nor was abduction which, in a child murder, is another necessary element laid down by the statute.
This distinguishes Huntley from other notorious child killers such as Robert Black, for example, who has been told he will never be released.
In the case of serial killers such as the Yorkshire Ripper, Peter Sutcliffe, Denis Nielsen and Rose West, it is the fact that more than one murder was committed which earned a whole life tariff.
In saying that the appropriate starting point was 30 years, Mr Justice Moses was reflecting both the spirit of the 2003 Act and public revulsion at child murder.
Aggravating factors, such as Huntley's callous behaviour and lack of remorse pushed that up to 40 years.
But it is clear from the judge's comments that, although he did not impose a whole-life tariff, he does not envisage Huntley being freed at the 40-year mark.
That decision will be for the Parole Board which will take the judge's views into account as well as assessing the risk to the public of releasing Huntley on life licence.
Criminal barrister, Jeremy Dein QC said: "To all intents and purposes, this amounts to a whole life tariff in my view."
Though a long stretch by any standards, Huntley's tariff is still 10 years short of that imposed on four other child murderers.
Roy Whiting, who abducted and killed Sarah Payne in 2000, Howard Hughes, Timothy Morse and Brett Tyler have all been told they must serve at least 50 years before the possibility of parole.
This reflects a steady increase in the tariff for mandatory life sentences over the last decade or so and helps explain why England and Wales has more life sentence prisoners than Germany, France, Italy and Turkey combined.
The Prison Reform Trust said that the growth of such long sentences puts enormous pressure on the prison system and risked "institutionalising people".