The mother of murdered baby twins Chris and Cru Kahui, not their father, caused their fatal injuries and confessed to doing it, defence lawyers for Chris Kahui have told the High Court in Auckland.
Defence lawyer Lorraine Smith made the allegation during her opening remarks on the first day of the trial of Chris Kahui, who is charged with the murder of his sons.
The twins died on June 18, 2006, within about 14 hours of each other, at Auckland Starship Hospital after they were admitted to Middlemore Hospital on June 13.
A jury of seven men and five women was sworn in this morning, for a trial which is expected to take seven weeks.
More than 70 witnesses are expected to be called for the Crown while the defence is expected to call about 40.
Mrs Smith said the jury would hear from a witness who heard Macsyna King confess to hurting the twins, months after Kahui had been charged.
Kahui did not hurt his sons and there was no direct evidence or witnesses to support the Crown case, she said.
Earlier crown prosecutor Simon Moore QC warned the jury the trial would be long and arduous. His opening address lasted more than two hours this afternoon before a packed public gallery.
Mr Moore said whoever inflicted the injuries did so deliberately.
"There is no way the injuries to either twin, let alone both, were caused by an accident."
Mr Moore said a medical expert would testify that "each twin was grasped around the chest and squeezed so tightly, the ribs popped".
The twins were "slammed onto a firm, unyielding surface", like a wall, floor or mattress, he said.
The twins were injured by the same person, about the same time, with "extreme force".
Whoever had hurt the twins "must have known what they were doing and the outcome".
Mr Moore said Kahui was the only person who had the opportunity to inflict the injuries after he was alone with the twins in their room.
"It would not have taken long to do, a minute or two or much less."
Timing was crucial to the case, he said.
Kahui had fatally hurt the twins between their last normal feed on June 12, around 5pm to 6pm, and 9pm when CPR was performed on one of the twins who had turned blue, he said.
Mr Moore said Ms King could not have hurt the twins, as she was not at home when the fatal injuries were sustained.
Ms King had gone to visit her sister Emily on June 11, the day before the twins were taken to hospital despite Kahui not being happy that she was going out, he said.
Ms King went to the home of Kahui's father, Banjo, and planned to stay the night but about midnight an "agitated and angry" Kahui arrived on the door step, ordering her back to their South Auckland home to look after the twins, he said.
"She told him bluntly where to get off and that she would stay where she was and he could look after the twins."
Ms King returned to their home in the morning, after first taking their son Shane to hospital because he was unwell but told Kahui she was leaving again, saying she needed time out, he said.
Kahui was not happy but Ms King was adamant, Mr Moore said.
During the course of the day, friends and relatives visited the house but it was not until a few minutes after Kahui went into the twins' bedroom alone about 9pm that it was noticed Cru had turned blue, he said.
After a discussion among family it was decided not to call an ambulance but to look for Ms King instead.
Kahui spent that night sleeping in the twins' nursery.
"The next morning there wasn't a peep from the twins.
"Of course, we know why."
When Kahui was interviewed by police he was at best misleading and at worst untruthful, Mr Moore said.
The trial continues tomorrow when the Crown will call medical experts.