Convicted double-murderer Mark Lundy has won the right to have his appeal heard by the Privy Council in London.
Mark Lundy is serving a life sentence for the murder of his wife Christine and seven-year-old daughter Amber at the family's Palmerston North home on 29 August 2000.
In 2002, the Court of Appeal threw out his case and increased his minimum non-parole period to 20 years.
Lundy's lawyer David Hislop, QC, told Radio New Zealand's Nine to Noon programme on Thursday he will ask the council to look at scientific evidence given by the Crown in Lundy's trial and they will show that this was unreliable.
Speaking from London, Mr Hislop said this concerns, in particular, scientific methods used to identify alleged brain tissue matter on Lundy's shirt.
He said it was the first time the United States expert called by the Crown had used the technique, which allowed samples to be lifted from slides. Mr Hislop described it as essentially an experiment.
The lawyer said this evidence played a dominant part in the conviction, and if the Privy Council came to the view that the science was unsatisfactory, the conviction would be overturned.
Mr Hislop said there are also grounds for appeal relating to the alleged time of death, which was based on the contents of the victims' stomachs.
The Privy Council appeal is set down for three days during the week starting 17 June.
Australian-based lawyer Keith Becker was part of the defence team which unsuccessfully appealed in 2002 against Lundy's conviction.
Mr Becker said the case for the upcoming Privy Council appeal is on safe ground, as issues bought up by Mr Hislop are the same as those flagged by the appeal team over a decade ago.
The evidence on time of death and some other scientific expert evidence has always been wrong, he believes.
Tragedy 'being brought up again'
Christine Lundy's brother Glenn Weggery said he was disappointed to have found out about legal developments through the media.
He told Morning Report Lundy has the right to pursue all his options but it appears no one cares about the victims and their family who have to deal with the tragedy being brought up over and over again.
"We're trying to move on with our lives and let Christine and Amber rest in peace and it's just not been allowed to be done."
Mr Weggery said he and his family cannot afford to go to the hearing in London, but would do if they could.