The offer of a $50,000 reward to solve the case of Tuitania Barclay is just another ''tool in the toolbox'', police say.
The reward would be paid for information leading to the discovery of Tuitania (Tania) Marama Barclay - or her body - if that information led to the conviction of an offender.
Detective Senior Sergeant Malcolm Inglis, the relieving head of the Dunedin CIB, confirmed immunity from prosecution would be considered for any accomplice, but not the principal offender.
Operation Tui was a ''big inquiry'', with three detectives working on the case for more than a year.
''We want to get closure for the family.''
Ms Barclay was last seen on September 17, 2002, at her home in Wakari, Dunedin.
''Someone out there will know something about the relationships she was in and what happened around October-November 2002, when she went missing.''
The reward offer had to be signed off by Police Commissioner Mike Bush.
Police treated any follow-up questions on the use of rewards as an Official Information Act request.
They have previously declined to provide details of any payments as ''it would be likely to prevent members of the public coming forward in the future''.
Despite being used infrequently, there are no ''caps'' on reward offers, which are only used in conjunction with other police investigation methods.
The $50,000 reward offer for information relating to the Tuitania Barclay case closes on January 1, 2015.
Rewards
Cases where rewards have been offered in now-solved investigations
• Sara Louise Neithe, of the Hauraki Plains, was murdered on March 30, 2003. A $20,000 reward was offered for information or evidence leading to either her location or the conviction of a person responsible for her death, or the location of her Honda Civic car. The reward was later increased to $50,000.
• Nicholas Pike was last seen alive on March 15, 2002, in Mt Maunganui. A $50,000 reward was offered on July 1, 2007.
• Ngatai (Mellory) Dallington was last seen alive in Christchurch on December 18, 2008, and a $50,000 reward was offered.
• Grant Trevor Adams was last seen alive in Tauranga in November 2005, and a $50,000 reward was offered.
• Darrel James Crawford was last seen alive in Tauranga in August 2007, and a $50,000 reward was offered.
• William Taikato was last seen alive in Tauranga on December 19, 2007, and a $50,000 reward was offered.
Source: New Zealand Police
