Top New Zealand lawyer Nigel Hampton QC believes that in the event of a hung jury in the David Bain retrial, a further trial would be likely.
"If this were a hung jury, then normal practice would be for the Crown to apply for a retrial and for a judge to say it should go ahead," he told the Otago Daily Times.
He believed in this case the Crown would seek a retrial.
"They would say we are trying to prove this man killed five people, which would make him the most serious mass murderer in New Zealand's history still alive and we want to continue to prosecute."
Cost would not come into it.
"How do you measure the cost of justice? It would be an extraordinary decision if a judge said otherwise."
A decision would normally be reached within a few weeks of a hung jury.
The case would be interesting, because under new laws, after a certain time a majority verdict was enough to convict or acquit.
However, there would likely be reluctance to do so in such a case, because it was so important.
"It would be a bold move to take a majority verdict, given the scale of the crime and the public controversy around it.
"I think a judge would try and strive to get a clear and unanimous verdict whichever way it went."
In the event of a guilty verdict, David Bain is most likely to be sent back to jail at sentencing and may not get out for many years, Mr Hampton believes.
He said be believed David Bain would again be sentenced to five life sentences for the murders of his family, but they would remain on the terms of the sentence rules and processes in place at the time of the murders.
"Although the law and practice has changed a bit, I think it would be considered wrong to sentence him to a longer non-parole period than was imposed in the first place.
That would sort of have an element of retrospective punishment attached to it."
It was written in the Bill of Rights that a person should not receive greater punishment subsequently than they were facing at the time of their original crime or trial.
Bain served 12 years of a minimum non-parole period of 16 years before his convictions were quashed and he was granted bail in May 2007.
He believed Bain would have to complete the remaining four years of his non-parole period before he could apply for parole.
Given the history of the defence of David Bain, Mr Hampton said he would be "absolutely astonished" if the defence team did not appeal a guilty verdict.
In the event that he was acquitted, David Bain would have difficulty getting compensation unless he could prove he was innocent, said the Christchurch QC.
Proving on the balance of probabilities that a person was completely innocent was a different matter to proving beyond reasonable doubt they were guilty, he said.
Mr Hampton worked for eight years on the Rex Haig case, until Mr Haig was acquitted in 2008 after spending 10 years in prison after he was convicted in 1995 of murdering Mark Roderique.
Mr Haig's subsequent request for compensation was rejected by the government after a retired high court judge found Mr Haig had failed to show he was innocent of the crime with which he was charged.
A not guilty verdict did not necessarily exonerate the accused person of the crime, but indicated there was reasonable doubt they did it, Mr Hampton said.
The person applying for compensation had to prove on the balance of probabilities that they were completely innocent.
"The reality is, that's what [Bain's] got to do, and there might be some difficulties with that," he said.
