Victims of black cab rapist John Worboys have accused the Parole Board of failing to take account of "critical evidence" when reaching a decision to release him from prison.
Their lawyer told three leading judges at the High Court in London on Tuesday that the evidence related to "wider allegations" of offending against the serial sex attacker.
As Phillippa Kaufmann QC, for the women, outlined their case, 60-year-old Worboys, who now goes under the name John Radford, watched proceedings via video link from prison.
The barrister told Sir Brian Leveson, Mr Justice Garnham and Mr Justice Jay: "The Parole Board failed to take account of critical evidence - evidence that wasn't in its discretion to ignore."
The Parole Board should have taken into account "evidence relating to the wider allegations of Mr Radford's offending than the offences for which he was convicted".
Police believe Worboys had more than 100 victims, although he was only convicted in relation to some of them, the court heard.
Worboys was jailed indefinitely in 2009, with a minimum term of eight years, for drugging and sexually assaulting women passengers.
He became known as the black cab rapist after attacking victims in his hackney carriage.
Ms Kaufmann pointed out that Worboys had made a statement in which he denied committing offences other than those he was convicted of.
The QC told the judges that even putting aside the "failure" to take into account the wider allegations, "this is a decision that is irrational".
Ms Kaufmann said the Parole Board's reasons for believing Worboys no longer poses a risk to society included that he had "learned to be open and honest".
She said the board also considered his risk was reduced because of the fact he took "full responsibility" for his crimes, had "good insight" into his behaviour and had undergone treatment.
However, the barrister said police who investigated Worboys believed he had committed offences against 105 women.
She added that he often left victims "confused and disoriented" and with only a partial memory of their ordeal.
The judges are also hearing an action against the Parole Board by London Mayor Sadiq Khan.
As the two-day case got under way, Mr Khan said in a statement that it was his "top priority to keep Londoners safe".
He said: "I am morally and duty-bound to do everything within my power to protect them from harm.
"John Worboys presents a significant threat to Londoners' safety and on behalf of his victims and survivors, I felt I had to be involved."
The Sun newspaper is also taking part in the legal action after Sir Brian and Mr Justice Garnham gave permission last month to proprietor News Group Newspapers to challenge the Parole Board's refusal to publish its decision.
A temporary bar on Worboys's release, initially imposed in January by the High Court, is continuing pending the outcome of the proceedings.
Worboys is represented by Edward Fitzgerald QC, who will make submissions on his behalf during the hearing.