Police and supporters of David Bain are to re-examine crucial evidence in the case after an application by police to access original material.
Mr Bain spent 13 years in prison for murdering his family in Dunedin in 1994, but was found not guilty at a retrial in 2009.
A recent television documentary showed photographs which supporters say proved Mr Bain's father, Robin Bain, had powder marks on his fingers, indicating that he, not David Bain, fired the fatal shots.
Police argued that the marks were cuts and reiterated that Robin's Bain's fingerprints were not found on the gun.
Police also applied to the courts to access the originals of the fingerprints and have now been granted permission, allowing the evidence to be re-examined next week.