One of the country's most notorious killers allegedly raped and abducted a 14-year-old girl in a previously unreported case before going on to commit murder.
The allegations against Hayden Taylor, now 34, who is serving a sentence of preventive detention, only came to light at a Parole Board hearing last year.
The alleged attack took place four months before Taylor sadistically murdered pregnant teenager Nicola Rankin in September 1996 while he was on bail for raping former street worker Amanda Watt.
But police say they are powerless to prosecute Taylor, who will make his latest bid for freedom at a parole hearing tomorrow, because the woman didn't want to press charges.
Taylor forced 18-year-old Rankin to walk into the remote Riverhead Forest, 35km northwest of Auckland, and bludgeoned her to death with a spade.
Her body was found in a shallow grave with her hands bound behind her back and her underwear had been removed.
Taylor had just been released on bail for a strikingly similar attack on Watt in April, in which he threatened her with a knife, tied her hands behind her back and raped her in his car.
He drove her to Muriwai Beach, where he tried to force her into the sand dunes. However, fearing he would kill her, she managed to persuade him to return to the city.
Both Watt and Rankin's mother Carol only learned about the fresh rape allegation when it was cited by the Parole Board as a "concern" at a hearing last year. Both women are terrified about the prospect of Taylor being released.
Watt, who waived her right to anonymity as the victim of a sexual assault, pleaded for the woman to press charges.
She said: "I have a burning need to know she got justice, that she was believed, that she was not coerced.
"I need to know it was her decision not someone else's. I want her to come forward and re-lay charges against him - that will keep him in.
"This girl needs to find out he is due out again. I mean, if that shit happened when she was 14 - she wouldn't want him out."
Carol Rankin said she was still haunted by her daughter's vicious murder.
"It doesn't get easier; in fact, I find it quite traumatic actually," she said.
"This year has been pretty hard, I have been very down in the last few months.
"I mean, how many more years can we keep him in, that's the thing. Nicola was 18 when she died and you don't have these milestones - you don't have a 21st, you don't get a wedding - we didn't get our grandchild."
She said her "biggest fear" was that Taylor would reoffend if he was let out.
"There is nothing we can do to stop that."
Police said they could not comment on the historic rape allegations due to the Privacy Act.
But Detective Inspector Bruce Scott, Waitemata District Crime Services Manager, said officers continued to work with the victims and their families.
"Any prosecution decisions must take into account the wishes and best interests of victims and their families as well as the obligations of police."
Trail of offending
April 1996: Taylor kidnaps and rapes Amanda Watt who was working as a prostitute on Karangahape Rd, Auckland. He is released on bail.
June 1996: He allegedly abducts and rapes a 14-year-old girl. She does not want to press charges.
September 1996: Murders Nicola Rankin buries her in a shallow grave in Riverhead Forest.
November 1996: Taylor is sentenced to life imprisonment for Rankin's murder.
December 1997: He is sentenced to preventive detention for Watt's rape.
November 1 2010: Next parole hearing.