Police say the Privy Council's decision to reject double murderer John Barlow's last legal bid confirms the overwhelming strength of the prosecution case.
The court in London on Wednesday ruled Barlow's convictions for the 1994 killings of Gene and Eugene Thomas in Wellington should stand.
Barlow, 63, continues to maintain his innocence. He took his appeal against the convictions to the Privy Council, arguing that FBI evidence linking the gun and bullets used in the murder to him was unreliable.
On Wednesday, the Commonwealth's highest court dismissed the appeal. It found that, though some evidence may have been discredited, the conviction itself was sound.
Barlow twice went through trials that ended in hung juries, before finally being jailed for the murders in 1995. In August 1996, the Court of Appeal dismissed an appeal by Barlow.
The officer who headed the inquiry, Detective Superintendent Brett Kane, says he has not spoken to the Thomas family, but will be doing so.
Mr Kane says the Privy Council's ruling again backs up the work put into the case by a large and capable team.
He says the criticism is of one piece of evidence from one witness, among that of nearly 200 Crown witnesses.
Mr Kane says there have been advances in investigative and forensic science techniques, and perhaps with recent changes in majority verdicts the case might not have gone beyond one trial.
Family 'devastated' at ruling
Barlow's wife, Angela Barlow, is shocked that he has lost an appeal and says she will battle to prove his innocence.
She told Morning Report there is no evidence to show that he committed the crimes he was jailed for.
Barlow was turned down for parole earlier this year, after serving a minimum non-parole sentence of 14 years at Rimutaka Prison, near Wellington.
His sister, Anne Barlow, told Morning Report the Privy Council ruling had left her disgusted and devastated for her brother and his family.
She said he will now make sure he meets all the Parole Board conditions, so he can come out of prison and start putting his life back together.
Anne Barlow says her brother has been a model prisoner, but the justice system just cannot deal with people who continue to say they are innocent.