Key Points:

The lawyer for convicted multiple murderer David Bain says he has a very strong case to put before the Privy Council in a last ditch bid to get a retrial.

Auckland barrister Michael Reed, QC, heads the defence legal team for the five-day hearing starting in London on March 8.

In May 1995, Bain, then 23, was found guilty of murdering five members of his family on June 20, 1994 at Anderson's Bay, in Dunedin.

His mother Margaret, his father Robin, sisters Arawa, 19, and Laniet, 18, and brother Stephen, 14, all had .22 gunshot wounds to their heads.

Bain was arrested four days after making a frantic 111 call from the family home. Police responding to the emergency found him huddled in the house babbling incoherently.

Bain collapsed in the dock as guilty verdicts were read at the end of a 16-day trial presided over by Justice Neil Williamson at the High Court at Dunedin.

Three weeks later he was sentenced to life imprisonment with a minimum non-parole period of 16 years.

Justice Williamson has since died, Bain's trial lawyer Michael Guest has been struck off the role of barristers and solicitors for lying to a client and Bain has been incarcerated for well over a decade, but still he fights to clear his name.

He asserts he is innocent and that his father killed the family before killing himself while Bain was doing his early morning newspaper delivery run.

The attempt to clear his name has not been smooth, with failed bids for legal review. A bid for Royal Mercy was also declined.

Mr Reed told NZPA although Bain was due for parole in about 2010, applying for a retrial was still worthwhile.

"I'm sure if you thought you had been wrongly convicted, any day you saved would be good, and also, you would like your name cleared as a murderer."

Although the application was for a retrial, an even better outcome was possible, Mr Reed said.

"They can overturn the convictions, they can order a retrial or they can send us home -- dismiss the appeal, in other words.

"We have a very strong case but as with any court case it depends on the judges on the day."

Mr Reed said the material the defence team was putting to the Privy Council had already been put to the Court of Appeal, which did not grant a retrial.

"We're going to explain to the Privy Council what we think the Court of Appeal got wrong, which includes a whole lot of previously undisclosed evidence -- evidence that wasn't disclosed at the original trial and new evidence that's been discovered since the trial."

The defence team would present affidavits from 41 witnesses, including scientists, pathologists and experts who gave evidence heard by the Court of Appeal in Wellington, but not the original jury.

Questions raised on appeal were matters relating to:

* the time a computer in the house with the message: "Sorry, you are the only one who deserved to stay" was turned on;

* whether the spectacle lens found in Stephen Bain's bedroom got there at a time or in a way unrelated to the murders, or whether there was at least a reasonable possibility that was the case;

* whether it was possible bloody fingerprints found on the murder weapon and identified as David Bain's were put there sometime before the murders;

* whether the crown was correct to assert, as it had in its closing address at the Bain trial: "Only one person could have heard Laniet gurgling. That person is the murderer";

* the origin of bloody footprints in the house;

* the mental state of Bain's father Robin at the time of the killings;

* incest allegations which the defence argues form a motive for Robin;

* the likelihood of Robin having killed himself;

* scientific evidence pointing to Robin as a killer.

Bain has been granted Legal Aid because the Privy Council has granted leave to hear the case, but Mr Reed said he would not be getting rich off taxpayers.

"You're paying me a miserly fee," he said.

"When we first went to London to get leave to be heard, we funded that ourselves. We got an order for costs, which helped us out, but we did that on a voluntary basis initially."

Mr Reed has never met Bain, but would if Bain so wished.

"There's no need for me to meet him, these are all matters of law and things."

Mr Reed said the Privy Council, as the ultimate appeal court of New Zealand for this case -- new cases go to the Supreme Court in Wellington -- would see him appearing as a QC, exactly as if it were a local court.

"They are sitting in the New Zealand jurisdiction with five Law Lords."

There was no way of knowing how long it would be before the Law Lords made their decision after the hearing.

Other members of the defence team are Wellington lawyer Paul Morten, and renowned Bain supporter, former All Black Joe Karam.

Mr Karam has maintained an unwavering belief in Bain's innocence and has been credited with keeping the case alive.

The solicitor general and deputy solicitor general will represent the crown.

In 166 years, only 10 New Zealand criminal cases have been granted full Privy Council hearings.

Of those six were dismissed, three were allowed and one was withdrawn by the appellant, Ministry of Justice statistics sho w.