Oberon parents guilty of murdering boy, 3, after weeks of abuse

A mother and stepfather have been found guilty of murdering their three-year-old son after subjecting him to a horrific regime of physical and psychological abuse.

The pair claimed the boy died after tripping over a dog leash during a family trip to the park, but a jury found them guilty of murder in the NSW Supreme Court onTuesday after two-and-a-halfdays of deliberation.

Their trial heard that the boy had been happy and healthy living with relatives in Sydney, before he moved to the home of his mother and stepfather in Oberon, in central western NSW.

Seven weeks later - August 6, 2014 - he was pronounced dead.

The court heard that the couple made admissions to police that they had inflicted horrific abuse on the boy during the short time he was in their care, including beating him repeatedly with a wooden spoon, taping a ball to his mouth and putting him into a portable cooler filled with ice and closing the lid.

In the days before the boy died, his mother admitted she had rammed a cupboard door into his head because she was "so pissed off" and "just wanted to get some sleep".

"He was standing up against the wall and I just kept poking his forehead because he wouldn't stand up straight and his head kept banging on the wall," the court heard that his mother told police of another incident that happened days before he died.

"I don't know what I did to him because I was really pissed off but he ended up in like a catatonic state."

But their defence barristers argued that the pair were not responsible for the injuries that caused the boy's death. They claimed that the boy died after he tripped over a dog leash during a family visit to the park. It was a story they maintained from the first triple zero call.

The boy's cause of death was cardiac arrest and an autopsy detected multiple blunt force trauma injuries on his body, scabs on his face and serious injuries to his spine. The trial heard that there was conflicting medical evidence about whether the boy tripping, falling backwards and hitting his head could have caused the injuries that led to him going into cardiac arrest.

The Crown's case was that the pair fabricated the story to explain what happened to the boy and that he never went to the park that day. The mother, the Crown said, committed the act that killed the boy, but the stepfather was complicit in the murder.

"I had so many thoughts about killing [the boy] because I loved him but I just didn't connect with him," the mother told police after he died.

"Don't get me wrong, I did love that boy ... but there was a part of me that hated him because he looked like his father, because he is his father's child."