Police are calling for greater powers to take DNA after catching a "cold case" rapist from a sample taken after a minor traffic incident.
Pop Tanupou E'Moala Aholelei this week admitted the 2001 rape of a woman in Auckland's Parnell Rose Gardens.
The attack was front-page news andled to a big police inquiry.
But with few leads other than a DNA sample, the case was shelved.
In June last year Aholelei was interviewed by a constable after a car crash and - in what detectives describe as a naive decision - he volunteered a DNA sample.
At the national DNA database it was matched to the sample taken from the rape. Aholelei was arrested in August - almost five years to the day after the rape. His guilty plea in the Auckland District Court spared the victim returning from her new home in Australia to give evidence.
Aholelei's arrest was one of the first by the Auckland City police adult sexual assault team, the first specialist squad of its kind in the country.
Detective Constable Damian Espinosa said the victim had mixed emotions - traumatised by the ordeal but also relieved she would not have to relive it in court.
Privately, many police believe DNA should be taken from alleged offenders "on arrest", just as fingerprints or mugshots are. This is done in the United Kingdom.
Aholelei's sample was one of the 71,934 on the national DNA database.
Police national forensic services adviser Inspector John Walker said about 80 per cent of the 10,000 samples police collected each year were given voluntarily and the rest compelled through court order.
