'I killed my kid': jury hears dad's alleged confession

The Sydney man, who cannot be named for legal reasons, is facing trial after his wife left him alone with the child for 15 minutes and returned home to find the boy in need of serious medical attention.

"She saw the accused standing at the door holding (the baby) in his arms," said crown prosecutor Sally Traynor.

"The baby was floppy, pale and his eyes were staring up."

In front of a NSW Supreme Court jury, the man has pleaded not guilty to murder and the alternative charge of manslaughter.

The accused and his wife are Afghan nationals who were living together in a two-bedroom apartment after an arranged marriage when the tragedy occurred on June 27, 2020.

The wife, who also cannot be identified, left her son in the care of her husband to visit a nearby doctor for a blood sugar test required as she had been diagnosed with gestational diabetes while pregnant.

She realised she had left her mobile phone at home and returned to find her husband distressed and the baby in critical condition, the jury heard.

Neighbours were called and the family driven to a local hospital where the young child was resuscitated.

"I killed my kid," the man allegedly said in English soon after they arrived at the hospital.

Ms Traynor said police body-worn footage would be shown to the jury showing the alleged confession.

However, the exact words said are disputed by the man and his legal team.

While the infant was revived, his condition did not improve and doctors recommended that life support be turned off on July 20. The boy died later that night.

In a phone call recorded by police, the man's wife allegedly accused him of shaking the baby every hour causing the child to scream.

"You'll kill him, you'll kill him, you'll kill him," she said in the Afghan dialect of Dari.

She allegedly told her brother over the phone that she wanted to separate from her husband years before but hadn't been allowed to because of his reputation.

Medical examinations showed excessive bleeding in the space between the child's brain and skull, a shrinking of his brain caused by decreased blood flow, and numerous haemorrhages on his retinas.

Cause of death was determined to be due to complications from a head injury.

Ms Traynor said medical experts agreed these injuries were likely caused by "shaken baby syndrome" from an event occurring within 48 hours of the infant being admitted to hospital, and were unlikely to be the result of a fall.

One expert would say the child's brain experienced "significant rotational force" within the skull while another would say the symptoms emerged from a "non-accidental head injury," jurors were told.

The husband's barrister Nathan Steel told jurors his client did not dispute his son was injured but denied that he was the one responsible.

"There are issues in this trial as to who may have caused those injuries, and how and why they were caused," he said.

One possibility was that the infant could have fallen or been dropped, both of which would not have been intentional, Mr Steel said.

There was also doubt as to the timing of the injuries, the jury heard, as they could have happened days or even weeks before the boy was taken to the emergency department.

The trial in front of Justice Helen Wilson continues on Thursday.

Australian Associated Press