The Independent Police Conduct Authority (IPCA) will investigate allegations of police misconduct during their investigation into serial rapist Malcolm Rewa.
The announcement came hours after murder and rape victim Susan Burdett's brother said she would still be alive if police had acted on a complaint against Rewa made by another rape victim.
IPCA chairman Sir David Carruthers said the authority had "reflected on the information that has been raised over the past few days relating to this matter and has independently decided an investigation is warranted''.
"This will focus on the nature of the police investigation into the historical allegations of rape raised by a number of women and whether police should have identified the perpetrator during the course of their investigation.''
TV3's 3rd Degree this week revealed a woman, who was attacked in 1987, gave police Rewa's name but when they approached him he claimed to have an alibi, saying he was drinking with a mate at the time of the attack.
Police later tracked the mate down to Australia, but they did not talk to him.
Announcing the IPCA investigation, Carruthers said it would not consider matters in relation to Teina Pora, who was convicted of Burdett's slaying, that were currently before the court.
"We have listened to the conversations and discussions involving this matter and we have taken everything on board. It is not unusual for the Authority to re-evaluate a decision as new information comes to light," he said.
He said the investigation would be carried out by the authority's independent staff, including non-New Zealand investigators and others from different backgrounds with experience of rape and sexual abuse matters.
- © Fairfax NZ News