By Jon Silverman
Legal affairs analyst
Though individual sentences are a matter for the law, politics is never far away from the process.
Home Secretary John Reid has criticised the paedophile's sentence
The principle under which a judge will impose a lower sentence in return for a guilty plea was formalised by the Criminal Justice Act 2003 which also established the Sentencing Guidelines Council.
The aim was to address the postcode lottery in sentencing, to spare victims and witnesses the trauma of a contested trial and to save money.
Then Home Secretary David Blunkett was happy to claim ownership of the legislation as part of New Labour's drive to create a more efficient justice system.
Now his successor, John Reid, is discovering that legislative reform usually has a downside too. And, like Mr Blunkett, his instinct as a politician is to attack the judges.
The level of rhetoric hostile to judges emanating from government has created considerable tension
Attorney General Lord Goldsmith is said to be unhappy at Mr Reid's letter urging him to try to increase the sentence imposed on the paedophile, Craig Sweeney.
If so, it is a cumulative unhappiness, because this attorney general has probably been confronted by more ministerial interventions in judicial matters than any recent predecessor.
The chancellor, Gordon Brown, revealed background details of an accused man facing a terrorist trial. Mr Blunkett made remarks following the arrest of a terrorist suspect in Gloucester in 2003 which many lawyers felt to be prejudicial.
And the level of rhetoric hostile to judges emanating from government, from the prime minister down, has created considerable tension.
But home secretaries have always used their status as elected representatives to intervene in the law.
Michael Howard famously raised the tariff imposed on the young killers of James Bulger following a campaign to put pressure on him by the Sun newspaper.
Successive administrations have refused to abandon the mandatory life sentence for murder because they say it is a crime which society regards as uniquely heinous and that, as representatives of the public, ministers have a duty to reflect that concern.
When it comes to individual sentencing decisions, though, a home secretary has no formal role. It is for the attorney general to refer a sentence he considers lenient to the Court of Appeal.
the idea that judges ignore popular concerns about crime is simply not borne out by the facts
And, as recent figures show, in two out of three referrals, he is successful in getting the sentence increased.
And those who accuse judges of being soft on crime should consider that, according to the Home Office's own figures, the average sentence length increased by 6% to just over 17 months between 2004 and 2005.
Average times spent in prison for the most serious crimes, especially murder, have increased significantly in the last decade - which is one reason for the record prison population.
So, the idea that judges ignore popular concerns about crime is simply not borne out by the facts.