The Kahui twins died of natural causes according to a controversial medical opinion given to the coroner for an upcoming inquest into their deaths.

The report by Dr Damian Wojcik, a police medical examiner in Whangarei for 16 years, hypothesised that the 3-month-old babies died from Barlow's disease - or infant scurvy from a severe vitamin C deficiency - rather than Shaken Baby Syndrome.

Dr Wojcik has claimed that Barlow's disease could explain the bruises, subdural bleeding and fractures found in the bodies of Chris and Cru Kahui, who died in June 2006.

But the unorthodox report sent to the coroner has been dismissed by an independent pathologist and will not be aired as evidence at an inquest on the deaths of the twins due to be held this year.

Chief Coroner Neil MacLean, a District Court judge, confirmed that the medical opinion had been dismissed but declined to comment further.

All Crown and defence witnesses at the 2008 murder trial of Chris Kahui, who was acquitted, agreed that the twins were shaken to death and suffered multiple fractures.

Dr Wojcik told the Weekend Herald he was aware that his theory that the Kahui twins were not murdered would be treated with scepticism.

"It is controversial and I have to say some medical practitioners wouldn't believe a word of it."

But he said that extreme vitamin C deficiency could cause the haemorrhaging in skin, brain, and subdural spaces as well as the pathological fractures suffered by the Kahui twins.

"This is a hypothesis I mulled over for many months. When I submitted that report to the coroner, he had it peer reviewed and the pathologist basically doesn't believe a word of it."

Dr Wojcik said the forensic evidence showed that the twins did not suffer damage to the neck and spinal cord, which did not match the theory that they were shaken to death.

"This is quite a complex area and quite nuanced. I would want to try and advance the cause of truth and not end up in some ideological slinging debate with some of my medical colleagues.

"There are other explanations for pathological findings. You could make a case for an alternative hypothesis of death by natural causes, so I advanced that."

The Weekend Herald understands the Office of the Coroner was initially thrown by the natural causes theory but now considers it a "red herring".

Simon Mount - one of the Crown prosecutors at the trial - is now a barrister acting on behalf of the police at the inquest. He declined to comment on Dr Wojcik's claims but Lorraine Smith, defence counsel for Kahui, said she appreciated the time Dr Wojcik had taken to raise a theory with the coroner.

"His views may not be orthodox, but who knows what the position will be in 20 years' time? People rubbished Galileo and he was proven right," said Mrs Smith.

"But whoever, or whatever, killed the twins was definitely not Chris Kahui."

The inquest into the deaths of Chris and Cru Kahui has been delayed since a scheduled date in February. It is understood a large number of agencies will take part - including two district health boards, GPs, the Families Commission, children's commissioner, the Ministry of Social Development, police and the Crown.

Judge Maclean has previously said an inquest would take a wider view of the deaths and look at whether anything could be done to prevent similar events in the future.

However, the focus is likely to remain on debating who killed the twins rather than how to prevent further child abuse.

In the murder trial, Mrs Smith accused the twins' mother, Macsyna King, of murdering the babies and Kahui was found not guilty.

The police cannot reopen the investigation until new evidence comes to light, so a $50,000 reward has been offered by lobby groups Family First and the Sensible Sentencing Trust as an incentive for someone to come forward.

* Infant scurvy is sometimes referred to as Barlow's disease and is caused by a lack of vitamin C.
* While cases are rare, Barlow's disease is fatal if left untreated. Doctors overseas have claimed that toxic histamine levels, caused by the vitamin C deficiency, can be misdiagnosed as Shaken Baby Syndrome.
* There is no convincing evidence to back up the theory that it has been misdiagnosed as Shaken Baby Syndrome.