A High Court judge is to rule on whether Soham murderer Ian Huntley will spend the rest of his life behind bars.
Huntley was convicted of the schoolgirls' murders in 2003
The former school caretaker, aged 31, received a mandatory life sentence for the 2002 murders of Jessica Chapman and Holly Wells, both 10, in Soham, Cambs.
Trial judge Mr Justice Moses will now decide if that will actually mean life.
Huntley's offences predate the 2003 Criminal Justice Act, which imposed "whole-life" terms for certain multiple murders and child murders.
The minimum term served by people given life sentences for other murders used to be set by the home secretary, but Law Lords decided in 2002 this breached the European Convention on Human Rights.
Judges now recommend the minimum tariff.
'Few worse crimes'
Huntley could become one of more than 20 murderers, including Yorkshire Ripper Peter Sutcliffe and Moors murderer Ian Brady, who will never be freed.
Mr Justice Moses told him during sentencing: "There are few worse crimes than your murder of those two young girls."
Huntley is currently being held at Wakefield prison.
It emerged during his trial that he had been previously accused of rape and of having sex with underage girls.
His former girlfriend Maxine Carr was jailed for three-and-a-half years for conspiring to pervert the course of justice.
She was freed from jail and given a new identity in May 2004.