KEY POINTS:
As far as murder mysteries go, it's right up there with the best of them. A mystery Russian, a body in a cupboard, little if any DNA evidence - and one big nagging riddle.
Nine years on, few New Zealanders can probably recall the name Kayo Matsuzawa. Granted,
there was nothing extraordinary about her - just another nondescript face in the crowd.
When her naked and decaying corpse was found dumped inside a utility room off a stairwell in an Auckland city building on September 22, 1998, there was no outrage, no outpouring of grief.
The case generated the odd headline, but, before long, the murder - and Matsuzawa - were forgotten.
Police went about their job trying to find the killer but, with little public interest in the case, the trail soon went cold. Understandably for Matsuzawa's family, that one burning question remained - who killed Kayo?
The answer to that question could lie in a number of theories being promoted by an investigative journalist and the maker of the new television series The Investigator. Bryan Bruce may not have found Matsuzawa's killer, but he has opened up some new lines of inquiry, either neglected or ignored during the original investigation.
And intriguingly, police appear to be taking Bruce's claims seriously.
The officer heading the inquiry, Detective Senior Sergeant Simon Scott, recently travelled to Japan with Bruce to investigate some of Bruce's theories around the case, and while he wouldn't go as far as to say police were close to a breakthrough, he did offer some hope the killer would be found.
"Mr Bruce has come up with several theories which may, in time, prove correct," Scott said.
The Herald on Sunday was forced to sign a confidentiality agreement which prevents us from revealing everything Bruce found, including what could be a crucial piece of new evidence in the case. There is also the strong possibility new DNA technology could play a part in finding the killer.
"The killer missed something, that's for sure," Bruce said.
He was confident the killer could be one of "only a handful of people" - and possibly someone still living in Auckland.
What is certain is that Matsuzawa died an awful death.
The 29-year-old arrived in Auckland on September 11, 1998 after a year working in Christchurch. She checked into a backpackers' hostel in Fort St and then vanished without trace not long afterward.
Eleven days later, her naked, decomposing body was found inside a fire alarm cupboard off a stairwell which connects the BNZ Tower to the Centrecourt building in downtown Queen Street.
There was proof of murder, but no motive.
Some of her belongings, including her passport, were found five days later by a rubbish collector in a rubbish bin on the corner of Mills Lane and Albert St.
At the time, police were unable to determine the exact cause of death, and, because of the decaying state of her corpse, there was no way to tell whether she had been raped.
On the surface, it appeared the perfect murder.
Police focused their initial inquiries on the BNZ Tower and Centrecourt, interviewing more than 100 people, including Asian students at a language school, all of whom had electronic security access to both buildings. But those inquiries turned up more red herrings than firm leads.
The doors to the BNZ Tower and Centrecourt building are controlled by two separate computer systems which means those entering need either a personalised data entry key or swipe card. Oddly, the computer records from the night Kayo was murdered were missing, and to this day have never been located.
If Bruce's theories are correct, the killer is someone who would have had easy after-hours access to the BNZ Tower and Centrecourt and knowledge of the alarm system and stairwell leading to the cupboard where Matsuzawa was found. They also would have had a key to gain access to the cupboard or at the very least carried with them a screwdriver to force the lock.
But more significantly, that person would have had had access to the BNZ cardex printouts and knowledge of how to delete files from the computer which held the data entry key information in the Centrecourt building.
One suspect at the time had been a mystery Russian man in his 50s who was staying at the backpackers hostel and had earned the name "KGB" because of his prying ways. He left for Australia a few days after Matsuzawa's body was found and further eluded police by heading to Europe.
However, he doesn't fit the profile Bruce has compiled of the killer, and is believed to have since been eliminated as a suspect.
Based on Bruce's claims, the evidence tends to point to someone working for the firm providing security for the BNZ Tower and Centrecourt building. When asked to comment about the possibility someone from the security firm was responsible, Bruce said "next question", while Scott said security firm staff from the outset co-operated with the homicide investigation.
Bruce said one thing was certain: The killer was "a calculating meticulous sort of person".
He had to be "forensically aware" given how well he'd covered his tracks and was probably familiar with police procedures either because he had had a run-in with the law or because his job involved "crime detection".
The killer would also have had intimate knowledge of the rambling rabbit warren of a building given where Matsuzawa was found.
Bruce has two theories about how Matsuzawa came into contact with her killer, someone he thought may have gained her trust before murdering her.
She could have met him when she was heading back to the Fort St hostel on September 11 or sometime during the day when she was outside the Centrecourt building or BNZ Tower.
Asked whether police were now restricting their inquiries to "a handful of people", Scott said, "There have been several people of interest in the inquiry, but there has never been enough evidence to charge anyone with Kayo's murder.
"There are aspects of the homicide investigation that we prefer to keep confidential in order to maintain its integrity and that of any subsequent prosecution that might develop."
Scott also defended the work of the inquiry team, saying homicide investigations could be very complex and complicated.
Operation Net had been both those, and police were satisfied the initial phases of the operation were handled "robustly and according to accepted best practise procedures".