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Guide to the criminal justice system


Government Ministries and Agencies

The Criminal Justice System comprises a number of agencies each responsible to a government department.  The Ministry of Justice oversees the work of HM Prisons and Probation Service (HMPPS), covering prison and probation services; and HM Courts Service. The services which HMPPS are accountable for include HM Prison Service, National Probation Service, and Community Rehabilitation Companies.

The Home Office has responsibility for the 43 police forces in England and Wales and the Attorney General has responsibility for the Crown Prosecution Service.

Key roles in the Criminal Justice System 

Police are responsible for keeping the peace and investigating offences reported to them. They provide information and advice to the Crown Prosecution Service about the alleged offence(s) committed by individuals.

Crown Prosecutors are responsible for deciding whether there is sufficient evidence to charge and prosecute an alleged offender.  They also make representations to magistrates regarding suitability of bail prior to a trial or sentence hearing. If an offender is charged the CPS is responsible for prosecuting the offence in court.

Magistrates deal with cases in the magistrates courts including hearing trials.  They usually sit in panels of three (known as the bench) and one of them is the chair of the bench.

Judges deal with cases in the Crown Court.

Defence lawyers are responsible for representing defendants accused of an offence. 

Probation officers provide information and assessments on offenders appearing before the courts.  They also have responsibility for supervising offenders on community orders and post-release licenses. 

Prison officers are responsible for the security and welfare of prisoners in their establishments.   

The Courts 

The courts are divided into Magistrates Courts and Crown Courts.  All cases are initially heard at the Magistrates Courts.  There are some offences that are less serious and can only be dealt with at this level. There are other offences which can be heard at either the Magistrates or Crown Courts, and some are so serious that they can only be dealt with by the Crown Court. Magistrates are volunteers who have been trained and have the support and advice of legally qualified court clerks.  Judges sit primarily in the Crown Courts and are qualified barristers who have been appointed to the judiciary.

The Process

Almost all criminal cases begin with an offence being reported to the police. After investigation they will arrest an alleged offender and if there is sufficient evidence they will recommend to the Crown Prosecution Service that the individual(s) are charged with a specific offence. There will also be a decision made as to whether the defendant is held in custody pending his/her trial or whether it is safe to release him/her on bail until the case is dealt with. This decision is made by the magistrates based on information provided by the National Probation Service (through pre-sentence reports), defence solicitor, and the Crown Prosecutor.

The Sentence

If a defendant pleads guilty, or is found guilty after a trial, the magistrates or the judge (depending on the seriousness of the offence) imposes a sentence. It is often the case that the National Probation Service will have been requested to prepare a Pre-Sentence Report on the defendant and the information, assessments, and recommendations in the report will be used to help the magistrate or judge arrive at a decision. Generally, the range of sentences that can be imposed include:

  • Conditional discharge – no further sanction so long as the offender stays out of trouble for the duration of the discharge period;
  • Fine – the level of the fine is usually related to the seriousness of the offence and must be paid within a set period of time;
  • Community Sentence – this places the offender under the supervision of the probation service and there will be a range of requirements that must be completed (e.g. attendance at group programmes, performing Unpaid Work, residing at a specific residence, etc.).  Supervision can last from 6 months to 3 years depending on the seriousness of the offence.
  • Suspended Sentence – a prison sentence will be imposed but suspended for a defined period of time.  As long as the offender stays out of trouble there is no further sanction;
  • Custodial Sentence – magistrates can only impose custodial sentences for up to 12 months.  Only judges in the Crown Court can impose longer sentences including Life Sentences for very seriousness offences such as murder or manslaughter.

Release from prison

All those held in custody, with the exception of a very small number who have received ‘whole life tariffs’, will be released at some point. 

  • Those sentenced to less than 12 months are released after serving half of their sentence are subject to supervision by Community Rehabilitation Companies (from June 2015). 
  • Those serving between 12 months and 4 years are released at the half-way point in their sentence and are supervised on license until the three quarters stage of their sentence. 
  • Those sentenced to more than 4 years are eligible to apply for parole at the half way stage of their sentence. If successful they are then supervised until the ¾ stage of their sentence. If not successful they are released at the ¾ stage and are ‘at risk’ until their sentence ends. 
  • For those sentenced to Life imprisonment they are only eligible for release after their ‘tariff’ (the minimum period of punishment specified by the sentencing judge) has expired.  Release after that point is dependent on the level of risk presented by the prisoner and a satisfactory resettlement plan.


Probation services are delivered by the National Probation Service, and 21 Community Rehabilitation Companies covering each part of England and Wales.

The National Probation Service (NPS) oversees the writing of all Pre-sentence reports, conducts all initial risk-assessments, and manages offenders who are deemed to be of high risk of harm to the public.

Community Rehabilitation Companies (CRCs) are responsible for the management of offenders who are assessed as low to medium risk of harm to the public.

Probation staff work in a variety of roles and organise and manage the different elements of community orders including Unpaid Work, group work programmes, and individual supervision and interventions. They also work with other public, private and voluntary organisations to provide offenders with help with accommodation, employment and education, drug treatment, and debt advice.   

HM Prisons and Probation Service

Within England and Wales, it is responsible for:

  • running prison and probation services
  • rehabilitation services for people in our care leaving prison
  • making sure support is available to stop people reoffending
  • contract managing private sector prisons and services such as:
  • the prisoner escort service
  •  electronic tagging

Through HM Prison Service: it manages public sector prisons and the contract for private prisons in England and Wales. Through the National Probation Service: it oversees probation delivery in England and Wales including through community rehabilitation companies.

HM Prison Service 

There are 142 prisons in England and Wales. Currently the prison estate is being reformed, with some men's prisons, and all women's prisons, being termed 'Resettlement Prisons'. The ambition is that these designated prisons will provide more focussed resettlement for offenders who live in the local area, and are nearing their release date (approximately four months before release). These prisons will work with Community Rehabilitation Companies and the National Probation Service to support resettlement. 

The prison estate is broadly categorised according to the level of security each provides.  

The High Security Estate (8 prisons) hold the most dangerous prisoners - Category A prisoners. 

The rest of the prison estate comprises Category B prisons, Category C (training) prisons, Category D (open or resettlement) prisons. There are some Category B prisons which function as remand prisons, holding prisoners appearing before the courts for either trial or sentence. Prisoners serving sentences of less than 12 months usually remain in remand or local prisons.

Depending on the length of sentence and the type of offence, prison regimes will include opportunities for training, education, drug treatment, and help with resettlement back into the community. For prisoners serving longer than 12 months there is an expectation that relevant prison staff will liaise with the probation service in the prisoner’s home area to implement plans for effective resettlement.

More information 

You can find out how the voluntary sector is involved in the Criminal Justice System here, and find organisations working with offenders here.