Police to reinterview Kahui twins' family

Police say Chris and Cru Kahui died of blunt-force trauma caused by a blow to their heads.

Police plan to re-interview the family of Chris and Cru Kahui following the discovery that both boys suffered broken ribs sometime before the head injuries that claimed their lives.

Police have also learned that the 3-month-old twins died from brain injuries possibly caused by a blow to their heads, not from "shaken baby syndrome" as initially thought.

Detective Senior Sergeant John Tims said the new information on the injuries came from a verbal briefing by the pathologist.

"From the post-mortem the pathology evidence indicated shaken baby but with further analysis it's been revealed that both twins received blunt-force trauma."

It would have been caused by a blow to the boys' heads, or their heads hitting a solid object, but he could not say what kind of weapon, if any, was involved.

One twin also had a broken femur, which the pathologist said occurred at the same time as the head injuries.

Mr Tims said the pathologist also found that both twins had suffered fractured ribs.

He was unable to expand on what caused the rib fractures but said they occurred earlier than the head injuries. He could not specify when.

Mr Tims said the investigation into finding the person responsible for the fatal injuries was progressing well.

Police would now re-interview family members to discuss the updated pathology findings.

He was confident the killer would be found and had just one message for whanau members, many of whom initially refused to co-operate with police.

"We don't know who inflicted those injuries but what we do know is that we are not looking at a stranger. It is a family member of the twins. The death of Cru and Chris Kahui will not go away. The investigation into their death will not go away.

"I think it's important that [the whanau] realise they must come forward and tell the whole truth and as this investigation continues the skeletons of the family are being uncovered."

Mr Tims said he appreciated the public's support and patience.

He asked for that patience to continue, especially given the quick arrests in other homicides, such as the murder of Tony Stanlake.

"My colleagues around the country have had some great results in the last couple of weeks, but while some homicide investigations take three or four days, some take 18 months. It can't be rushed."