Ian Huntley has been given a mandatory life sentence but the tariff - the minimum term he actually serves - has yet to be decided.
Until a year ago it would have been down to Home Secretary David Blunkett to decide the length the murderer stayed in prison.
But the system of tariff-setting is in the process of being changed.
From Thursday offences such as Huntley's will carry whole life terms.
Because Huntley's offence was committed in August 2002, his case is subject to transitional arrangements.
This means the minimum term that he will serve in prison will be decided by an appeal court judge - to be appointed by the judiciary - not the trial judge