Mr Smith, now 31, has pleaded not guilty to murder but guilty to manslaughter over the death of the baby and is facing an estimated four-week murder trial in Newcastle Supreme Court.

The prosecution say Mr Smith was alone with the boy during the two hours when he suffered numerous serious injuries, including a fractured skull.

But lawyers for Mr Smith say the boy's mother had repeatedly punched and shook the boy before leaving him with Mr Smith.

They say Mr Smith was holding the boy when he likely suffered a seizure from the earlier assault and slipped out of Mr Smith's arms, hitting his head on the ground.

Crown prosecutor Neil Adams, SC, said on Monday one of Mr Smith's neighbours in Fairfield Avenue was awoken about 4.30am on February 9 by a man holding a baby.

That neighbour gave evidence on Tuesday, describing Mr Smith as "a bit hysterical" while she was on the phone to triple-zero and trying to give the baby CPR.

The jury were played the triple-zero call, during which Mr Smith can be heard in the background crying and begging for the baby to breathe.

"Please stay with me bud," Mr Smith can be heard saying. "Please don't f---ing do this to me, man."

He could also be heard repeatedly yelling and swearing that the ambulance was taking too long to arrive.

The jury were also played body-worn video and audio of Mr Smith inside his home after the baby had been taken to hospital and police had arrived on February 9.

When a detective asks Mr Smith to tell him what happened, Mr Smith replies: "The baby was unsettled, I was trying to settle him. "I was trying to give him the bottle and he kept wriggling... he slipped out of me arms and he landed on the side of his head."

When asked if anything had happened to the boy between when his mother left and when he tried to feed him, Mr Smith replied: "What makes you say that? What do you mean? "He slipped, he slipped by accident. You're trying to f---ing say I dumped him on his head."

Police who went to the hospital and spoke with the boy's mother described her as "unemotional".

"[The mother] was on her phone most of the time and laughing with her sisters," a police officer said. "She asked me "have they got Jie at the police station for what he did to my son".

The trial continues.

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