The Privy Council has refused to hear an appeal by David Bain's legal team to have the murder case against him dismissed.
David Bain was released on bail in May 2007 after serving 13 years in prison for the murders of five members of his family.
His convictions were set aside by the Privy Council, and a fresh trial is due to begin early next year.
David Bain's lawyer Michael Reed had argued that a retrial in New Zealand could not be fair because many witnesses have died and evidence has been destroyed.
However the Privy Council in London said it was satisfied New Zealand courts could deal with the matter.
After the proceedings, Mr Reed said the outcome had been a victory, as the solicitor general gave an undertaking that every point the defence wanted to raise before the Privy Council can now be heard by the New Zealand court.
"We believe now, back in New Zealand, we can get a full and fair hearing that we always wanted," he said.
An application for a stay of proceedings will be held in the High Court in Christchurch in February, a week before the retrial is scheduled to begin.
At the Privy Council, Michael Reed, QC, told the court new forensic tests prove two key points of the original case against David Bain are incorrect.
He said tests showed the piece of skin found near the body of Stephen Bain, which the Crown said David Bain had lost in the struggle as he killed his younger brother, belonged to Stephen Bain.
And he told the court bloodied foot prints in the house were far too small to be David's and in fact matched the foot size of his father Robin.
Mr Reed also said the defence was unfairly disadvantaged as it could not test the computer at the centre of the original case, which no longer works.
A message had been typed on the computer at the Bain house which said "sorry, you are the only one who deserved to stay".
The timing of the computer's use was a key part of the original Crown case. It said David Bain typed the message in an attempt to frame his father.
Mr Reed told the Privy Council it is unfair that new technology cannot be used to test that computer, as it no longer works.
The Privy Council said all the defence arguments must be considered by the New Zealand courts before the scheduled retrial.
Legal aid bill
The cost of David Bain's defence is now well into the millions, making it the most expensive taxpayer-funded defence in New Zealand history.
His key supporter Joe Karam says the defence has already cost millions of dollars, all funded by the justice system, and the trial is still two months away. Mr Bain's original trial in 1995 cost $149,180.
Previously, the most expensive case paid for by the taxpayer was that of Scott Watson, which took 14 weeks, involved 400 witnesses and had a legal aid bill of $800,000.