Somewhere out there the killers of numerous New Zealanders are walking free, some for more than 30 years. But while the leads have ebbed away and the files have gathered dust, police are still determined to bring those killers to justice.
All cold case files murder files remain open until they are solved. Most have senior detectives assigned to them, ready to investigate any new information that comes to light.
In February 1962 Dunedin lawyer James Ward died from injuries he suffered when he opened a parcel from the morning mail that contained a bomb. Police have been unable to establish any motive for the murder, or make an arrest.
Welsh hitch-hiker Jennifer Mary Beard, 25, was strangled in a sexually motivated attack on New Year's Eve in 1969. Her body was found under the Haast River Bridge 19 days later.
A Christchuch police spokesman said the file remained open but there had been no new information provided to police for about 2-and-a-half years.
Mona Blades, 18, disappeared while hitchhiking from Hamilton to Hastings on Queen's Birthday Weekend in 1975. She was last seen getting into an orange Datsun and her body and belongings have never been found. Police say she was murdered.
"Obviously the file will remain open until someone is prosecuted for this. We will continue to assess the investigation on a regular basis,'' Detective Inspector Garth Bryan said in 2005.
In September 1983 Napier schoolgirl Kirsa Jensen disappeared while out riding her horse Commodore. The 14-year-old was last seen by an old gun emplacement near the mouth of the Tutaekuri River. Her horse was found tethered nearby, but there has been no trace of Kirsa since.
The officer in charge of the file Detective Sergeant Bryan Schaab once told the Herald that it was rare for new information to come to light after so long. But he was ever hopeful that he could resolve the case and close Kirsa's file.
Claire Hills' murder was described as one of the most callous in New Zealand history. The 30-year-old was abducted at traffic lights in Auckland in the early hours of the morning on April 28, 1998. Her abductor then took her to the top of Mangere Mountain in South Auckland, doused in her in petrol and set her alight.
"Operation Hills will be open until it is solved,'' said Detective Inspector David Lynch, who is now in charge of the file.
"Police receive fresh information from time to time, that information is investigated by a team of detectives appropriately.'' "For anyone that has information about what happened to Claire Hills that night - police urge them to come forward. It may be that circumstances have changed and due to this, they may be comfortable providing information. For the person/person's responsible for this, police don't just close cases, they work on them until they are solved. It's only a matter of time. A prime example of this is the 1979 homicide that was resolved (this week) - anything is possible.
In January 1998 the body of Ashburton teenager Kirsty Bentley was found in a paddock at the Rakaia Gorge, covered by branches. She had disappeared 18 days earlier and was killed by a blow to the back of the head with a heavy weapon.
Police still get calls from the public about Kirsty's death 13 years later, and have several hundred "persons of interest'' on their radar.
Detective Superintendent Peter Read said yesterday that all new information received was assessed to see whether it could take the case forward.
"Police and ESR do proactively review cases from time to time in terms of looking at the evidence that is held, and whether there are opportunities to re-test evidence in the light of ongoing advances in technology.
"We continue to ask anyone who has information on unsolved cases to come forward - we want to hear from them and we will follow through on any new information."