The broken ribs suffered by a 20-month-old toddler were caused by a "short, sharp delivery of force" in her bedroom, a murder trial has been told.
Forensic pathologist Dr Allan Cala told a Newcastle Supreme Court jury on Tuesday the attack on the toddler, who weighed only 11 kilograms, would have been very sudden, acting like a shockwave.
The toddler died from multiple injuries, including bleeding to the brain, broken ribs, a collapsed lung, lacerations to her liver and bleeding in her abdominal cavity.
Crown prosecutor Lee Carr SC said the toddler, who cannot be named, died after suffering a number of blows or kicks to the body.
Her bloodstained, size one pink Minnie Mouse pyjamas were later found in the bathroom.
Timothy Andrew Whiteley, 28, who has pleaded not guilty to murder, had been involved in a relationship with the toddler's mother.
The crown case is Whiteley was the only adult in the toddler's bedroom when she was attacked.
Whiteley claims he didn't cause the girl's injuries or take part in the attack.
Dr Cala told the jury on Tuesday he was given an account of what had supposedly happened to the toddler at a house in the Hunter region on June 19, 2018, before he performed an autopsy.
Dr Cala was informed Whiteley and the toddler's mother claimed they heard a loud thud come from the child's room just after 11am and found her on the ground with injuries to her face, suspecting they were caused by her falling to the floor and possibly hitting an object.
But when Dr Cala first examined the toddler he found she had suffered 13 separate injuries to her head and neck area.
A CT scan revealed the toddler had suffered multiple injuries Dr Cala believed had been caused by a "sudden, instantaneous force of a severe nature". Her broken ribs alone were the result of a "short, sharp delivery of force", he said.
Dr Cala said he was told the couple claimed the toddler was left to rest on a fold-out lounge over the next few hours after the fall.
The toddler was carried out to a car some time after 3pm when her mother went to pick up another daughter from pre-school.
Mr Carr told the jury the girl appeared on CCTV footage to be "floppy".
After returning home, the mother and Whiteley claimed they were outside having a cigarette at about 4pm when alerted to the toddler's deteriorating condition.
The couple went inside and noticed the toddler wasn't breathing and called an ambulance.
Paramedics attempted to save the girl but she was pronounced dead at 6.03pm at John Hunter Hospital.
According to the crown case, Whiteley and the girl's mother were the only adults inside the house with the toddler when there was a "thud-type bang" heard by a visitor just before 12.20pm.
Mr Carr said the toddler was carried from the bedroom area soon after in a clearly distressed state, unconscious and not responding but an ambulance was not called until 4.59pm.
The trial before Justice Stephen Rothman continues.