There will always be some differences between courts in their sentencing. An Inner London court is going to send more offenders to prison than one in Taunton. This week the Howard League released figures showing how some areas appear to imprison women more than others. The magistrates’ courts in Cumbria imposed immediate custodial sentences in 2.7% of cases in 2011 – four times the rate of areas such as Lincolnshire and Wiltshire. The phenomenon of ‘post-code sentencing’ has long been known in criminal justice. In 2007 the Ministry of Justice published a study which showed that adults who committed similar offences were treated less or more punitively in different courts.

There is similar evidence about the imprisonment of teenagers, where the proportion imprisoned (of those convicted) varied from 2 to 20% in different areas. Overall, evidence shows that justice is not meted out the same throughout England and Wales. But I would sound a note of caution. To really assess post-code sentencing you need to compare sentencing behaviour for similar offenders and similar offences, which is a very time consuming and expensive academic task. Rates of imprisonment, which the Howard League used here (and I did at the Prison Reform Trust) only indicate post-code sentencing – they don’t prove it.

Surprising places buck the trend. When I worked on the Prison Reform Trust’s Out of Trouble campaign we focussed on those areas which imprisoned more than others and encouraged the youth offending teams in those areas to reduce custody. Many of the areas with very high use of imprisonment – Liverpool, Manchester and Lambeth – were expected. But others weren’t. For many years Merthyr Tydfil in South Wales imprisoned proportionately more teenagers than any other area in the country. Way more than Newcastle, which had one of the lowest rates of imprisonment countrywide, including rural areas. Confronted with indications that their area might be particularly punitive, most youth offending teams said they had no control over sentences and most magistrates said custody was always a ‘last resort’ and they were sure they had more serious offenders in their area. The key was to acknowledge that statistics do not always paint a true picture and to persuade all that reducing custody systematically was possible. Leeds Youth Offending Team managed to reduce the number of teenagers imprisoned by a quarter through improving their assessments (pre sentence reports) of children at risk of being locked up and creating a better relationship with their court. Most of the areas with the greatest use of imprisonment managed to reduce it and now the total number of under 18 year olds in custody has been reduced by 60% in ten years.

Why is there post-code sentencing?

There should be more research into this but it looks as if particular areas and particular courts have sentencing cultures, which grow up over many years. Newcastle has a less punitive sentencing culture than many other big cities, but so does the whole of the North-East. In that area magistrates are used to dealing with troublesome youths in a particular way. Magistrates don’t go and observe courts in different areas, not pore over sentencing data. They are guided in their decision-making by sentencing guidelines, their legal advisor, their colleagues and of course, their own attitudes. Only if they are successfully appealed do they get any direct ‘feedback’ on their sentences.

Part of the answer is to give courts and sentencers better information, and better training. Magistrates are not the only people who sit in magistrates’ courts and are not solely responsible for local custody rates. District Judges sit in these courts too, and handle a lot of the more serious cases. Previous research has suggested that District Judges are more likely to imprison offenders than lay magistrates. So any figures about magistrates courts in a particularly area may be skewed by the number of District Judges in that area.

Will we ever have access to the information on sentences of every judge and every bench as we now do on surgeons in the NHS? I doubt it. Meanwhile it’s important not to play the blame game with custody rates. Magistrates and District Judges all want to reduce imprisonment. They need better information and effective alternatives to jail.