Police say they will review one of New Zealand's most famous unsolved crimes but will not reinvestigate the killing of Harvey and Jeanette Crewe.
The couple were killed at their Waikato farm in 1970 and their bodies dumped in the river, leaving behind a baby daughter.
Arthur Allan Thomas was convicted twice of murder and then later pardoned. No-one else has been tried.
Deputy Commissioner Rob Pope announced on Thursday that police will conduct a thorough analysis of the file after questions were raised by the couple's daughter, Rochelle Crewe.
Ms Crewe, who was 18 months old at the time of the deaths, wrote to Police Commissioner Howard Broad asking him to reopen the case.
She has told police she wants to know who killed her parents and why the two detectives accused of planting evidence were never charged.
Mr Pope says police are in contact with Ms Crewe and have appointed a senior investigator to go through the file.
However, he told Checkpoint it is too early to discuss whether police will investigate the theory that officer Len Johnston killed the Crewes.
"What we do need to do is focus on becoming conversant with the file, understanding it and, importantly, our prime obligation is to respond to Rochelle's quite reasonable questions."
Mr Pope says police will have to revisit boxes of information which date back 40 years, but could not say whether police will let Ms Crewe look at the file.
Review not enough, says Booth
Investigative journalist Pat Booth, who campaigned for the release of Arthur Alan Thomas, believes the review is just a gesture by police and not enough.
Mr Booth says he does not believe it will reveal who killed the Crewes.
"People are dead, people are away with the fairies, people have forgotten - reasonably enough.
"I had as close an overview of the case as anybody, I suppose, and a lot of years have gone past and a lot of things have happened."
Mr Booth says the review may throw new light on the way the investigation was handled.