A mother whose baby died of a severe brain injury says she would never harm her child and cannot explain how it happened.

Nyree Hopa and partner Robert Waru have both been questioned in a coroner's inquest about the death of their 7-month-old daughter, Staranise Waru, in February 2006, as police admit they have reached a "stalemate" in their homicide investigation.

Police say there have been inconsistencies in what the pair have already told them.

Coroner Richard McElrea yesterday made a preliminary finding that Staranise died of the effects of an inflicted physical injury, which pathologist Martin Sage said was consistent with being shaken or a "shaken impact".

Ms Hopa, called to appear at yesterday's inquest with Mr Waru, told the court that she did not know what happened to her daughter.

Under questioning, Ms Hopa and Mr Waru repeatedly answered that they could not recall events around their child's death, or opted not to answer on the basis they could incriminate themselves.

Staranise had been "grizzly" and "off colour" in the days leading up to her falling unconscious at her Christchurch home on the morning of February 16, 2006. After a bad night, Ms Hopa said Staranise did not seem right when she picked her up.

"She was, like, floppy. She wasn't looking at me so something was wrong ... she didn't really respond. I told her to wake up and then I tried to do CPR on her. I panicked. I didn't know what to do."

Ms Hopa called 111 and ambulance officers arrived to find Staranise unconscious and cold to the touch. Staranise was hospitalised, but her condition deteriorated and she was taken off life support and died two days later.

Mr Waru had only formed a relationship with Ms Hopa a couple of weeks before Staranise's death, and was staying a few nights a week with Ms Hopa and his daughter.

Detective Senior Sergeant Mike Johnson told the inquest that inconsistencies had emerged in earlier statements given by the parents, such as Mr Waru telling police that Staranise had banged her head on a door at a video store while he was with her.

Mr Johnson said video footage from the video store did not support this, and Mr Waru later changed his version of events to say that Staranise had hit her head on a car door.