Carmen autopsy challenge for pathologists

Carmen Thomas. Photo / Supplied.

Pathologists face a delicate task determining how Auckland mother Carmen Thomas was killed, an Australasian expert says.

The post-mortem examination of the 32-year-old South African's remains - found in plastic containers and concrete in a crude grave in the Waitakere Ranges last week - was due to be completed yesterday and results referred to the coroner.

Professor Jo Duflou, forensic pathologist and fellow of the Royal College of Pathologists of Australasia, said the post-mortem examination would have involved "great difficulty". He had never worked on a case like it in nearly three decades in the profession.

He said tools, and potentially heavy machinery, would have been required to pull off concrete that surrounded the remains - with great attention paid to doing "as little damage to the body as possible".

"You've got very hard material on the outside that's covered by something quite delicate on the inside," he said. "You've got to differentiate the peri-mortem injuries, the injuries that cause death, from the post-mortem changes, the decomposition ... deterioration of the body after death from the presumed dismemberment of the body ... and then the effects of concrete on the body."

Auckland's Chief Coroner, Judge Neil MacLean, said his office would now let the criminal process run its course.

When that was finished, the situation would be reviewed.

Police have refused to say if a murder weapon has been found or comment on associates of Brad Callaghan's understood to have helped with inquiries. The 32-year-old structural engineer, Ms Thomas' former partner, has been charged with killing her in her Remuera home, then dismembering and burying her body. He is the father of her 5-year-old son, Jack, who is in the care of a relative.

Grant Bennett, northern regional director of Child, Youth and Family, has not been approached for support.

"Prior to the arrest police asked Child, Youth and Family to be ready to become involved with Jack, if circumstances required it," he said. "In the end, the police were confident family members were able to provide the support the little boy needed."

Ms Thomas' mother, Teresa Scott, is understood to have arrived from South Africa.