The moments leading up to the death of a seven-month old who was found with unexplained bruising have been significantly disputed by the last two people to see her alive in a northern NSW unit.
The baby was in the care of her mother's partner when she left the Grafton complex for about 40 minutes just before lunch on December 4, 2015.
The partner, who along with baby AH and the mother cannot be named for legal reasons, had taken ice the night before the child died.
He says the mother left had left to pick up cannabis she later chopped up in the bathroom, minutes before her child died.
The pair's relationship had been volatile and the night before the death he kicked her out, but later felt sorry for her and she returned.
Whether Family and Community Service case workers should have stepped in earlier to prevent the baby's death, is also being investigated, counsel assisting the coroner Stephen Kelly said.
Numerous reports had been made to FACS in the months before the death, including one where the mother was drug driving for long stints with her other child in the car.
On December 4 the mother says she left her baby "laughing" and heard her giggling in the background during a phone call with her partner. When she returned home she saw her hand moving on the couch where she was sleeping.
But about 10 minutes later she returned upstairs to see her baby with froth coming out of her nose and started screaming that she wasn't breathing.
"I knew she was gone already," she later told police.
A neighbour who saw a man yelling for help in his yard ran over to find the baby unresponsive on the ground.
She helped the man perform CPR before paramedics arrived to find the baby cold to touch, with a blue head and lips, and mottling on the sides of her body.
The moments before the child's death have been inconsistently detailed in two police interviews by the partner and contradict the mother's account.
He originally told police "I gave her a bottle, she drank a little bit ... and I came back 20 minutes later," but no food or liquids were found in her body.
In his first police interview he was washing the dishes and vacuuming while the baby slept, but in his second interview he was downstairs cleaning the fish tank.
He also failed to disclose a heated text message he recently had regarding outstanding drug money owed, saying on the day he felt emotionally "fine".
The afternoon after the baby's death he sent messages to the mother saying he couldn't handle life anymore and that he wished she had never left the baby with him.
"I wish I could give my life to that beautiful little girl," the court heard he texted her.
A post-mortem could not ascertain the cause of death.
Child protection unit head at Westmead Children's Hospital, Dr Susan Marks, suspected "vigorous shaking" may have caused the head to whiplash and contributed to her death.
The autopsy also found two bruises on the baby's forehead and one on her left buttocks. A bruise on her right shoulder was said to be from a flu injection.
The week-long inquest continues before NSW Deputy State Coroner Elaine Truscott.
Australian Associated Press
