If an offender is convicted of murder then the judge must impose a life sentence. However, there are also circumstances in which a judge may impose a life sentence on an offender who has been convicted of an offence other than murder (although a life sentence will only be available to a sentencing judge in response to a serious offence).
With the exception of the small number of offenders, all convicted of murder, who have received a whole life sentence (on 31 December 2019 there were 64 people serving a whole life sentence) life sentence prisoners must serve a minimum term set by the sentencing judge before they can be considered for release by the Parole Board.
Life sentence prisoners are only released from prison when the Parole Board deems them safe to be released and are then subject to life licence. This means they can be returned to prison at any point to continue serving their life sentence if they either breach the conditions of their licence or commit a further offence. On 31 December 2019, there were 7,060 life sentence prisoners in prison.