Boy died from blunt force injuries: court

In the days leading up to the death of a two-year-old boy from multiple blunt force injuries, it would have been obvious to his mother that he was ill, the crown says.

Instead, they allege, she did nothing.

The boy, who cannot be named for legal reasons, was aged two years and seven months when his stepfather called triple zero on the afternoon of August 3, 2012 and complained the toddler was "limp".

Just over an hour later the boy was pronounced dead at Wollongong Hospital.

His mother, who also cannot be named, has pleaded not guilty to the unlawful killing of her son.

At the opening of her trial on Monday, Crown prosecutor Chris Maxwell QC told the Supreme Court the boy died from multiple injuries likely sustained in the days prior to his death.

The first, Mr Maxwell said, was a blunt force injury to his head which would have caused the toddler to lose consciousness, be in an "altered state" and possibly even have seizures.

Meanwhile, a blunt force injury to his abdomen would have caused the boy's gut wall to break and his bowel contents to leak out, causing symptoms including lethargy, paleness, pain and possible vomiting, the crown said.

"Even if the child had not complained, some or more of these symptoms would have been obvious to an adult carer," Mr Maxwell said.

While the crown does not allege the mother inflicted the injuries, they say her failure to take him to a doctor or hospital "substantially caused or accelerated the death of her son".

Mr Maxwell said it wasn't the first time the mother had failed to act.

Upon the boy's death, he was found to have a litany of injuries, including fractures to several ribs, a shoulder blade, his forearm and clavicle.

Mr Maxwell said the mother had not sought medical treatment on these previous occasions and evidence of the boy's living conditions would also point to neglect.

But her defence barrister, Winston Terracini SC, said the mother had made an appointment for her son to see a doctor on the Monday and that she was "doing the best she could".

"She wasn't the only carer. The child was regularly in the care and control of its natural father and stepfather," he said.

The trial continues.