Shaun Garry Johnson on trial for alleged stabbing murder of Steven O’Brien

A Newcastle man accused his mate of sleeping with his partner before slashing the father-of-seven’s throat at a Boxing Day gathering, a Supreme Court murder trial has heard.

Cheating allegations sparked an argument that saw a Newcastle man’s throat slashed during a Boxing Day barbecue, a Supreme Court murder trial has heard.

Steven O’Brien, 50, and his attacker Shaun Johnson, 38, were drinking with another friend, Billy Gee, when the stabbing occurred late on December 26, 2019.

Johnson is facing a judge-alone trial after pleading not guilty to murder. He previously pleaded guilty to a lesser charge of manslaughter on the basis of excessive self defence.

Steven O’Brien, 50, died after being stabbed at his Mayfield home in 2019. Picture: Facebook.

Mr Gee told the court the group had been drinking homebrew butterscotch schnapps at Mr O’Brien’s Mayfield home for “a good couple of hours” before the conversation turned to Johnson’s partner.

“Shaun said ‘my partner went out last night and I don’t know where she went’,” Mr Gee told the court.

“What did Steve say?,” Crown prosecutor Neil Adams SC asked.

“‘She didn’t come here mate’,” Mr Gee responded. “Shaun replied ‘well it’s my turn to go out tonight’.”

Mr Gee said Johnson then started “waving around” a weapon believed to be a knife.

“Next minute this fella jumps up and starts going sick,” he said.

“He went whack, slashed my mate’s throat. Steve said to me ‘he got me good’.”

Mr Gee told the court Johnson fled through a side gate and to his car, but the vehicle wouldn’t start.

He said he and Mr O’Brien chased Johnson, who then got out of the vehicle and told them “I’m sorry, I’m sorry, I’m sorry, I didn’t mean it”.

Steven O’Brien died after being stabbed in the neck.

At that time police arrived to arrest Johnson, while Mr O’Brien’s parents, who had been asleep at the property but woke to yelling, began first aid on their son.

In police bodyworn camera footage played to the court, Mr Gee told officers “the f**king motherf**ker stabbed him … he slit his throat”.

Mr O’Brien’s mother Beverly told police “I saw Steven running up the road and he said ‘he stabbed me mum’.”

Forensic pathologist Dr Hannah Elstub told the court the fatal wound, which severed Mr O’Brien’s jugular vein, would have been caused by a slashing or slicing motion, rather than a stab.

The trial before Justice Richard Cavanagh continues.

ON WEDNESDAY

‘I’ll Kill you’: Neighbours heard deadly stabbing

A neighbour said she saw a man washing blood from himself in her front yard in the moments after a Boxing Day dispute that saw a Newcastle man fatally stabbed.

Toni Foot told the NSW Supreme Court she heard someone yelling words to the effect of “you killed him motherf**ker, you’re dead” before a man stopped to use her tap.

Ms Foot told the court she heard the distinct sound of someone washing their hands but, when pressed by the defence, admitted she couldn’t be sure it was blood the man was cleaning.

Steven O'Brien with four of his seven children. Picture: Supplied.

Another neighbour, Leo Begarmo, told the court he too heard yelling including “I’ll f**king kill you … he’s been stabbed” before witnessing a man in Ms Foot’s yard.

Steven O’Brien, 50, died after being stabbed in the neck during the dispute at his Mayfield home, about 10.30pm on December 26, 2019.

Shaun Garry Johnson, 38, of Coopernook, is standing trial for murder, having pleaded not guilty to that charge but guilty to a lesser charge of manslaughter on the basis of excessive self defence.

In a frantic Triple-0 call played to the court, Mr O’Brien’s mother Beverly told the responder he wasn’t breathing and had changed colour.

While attempting CPR Mr O’Brien’s father Gordon could be heard in the background saying “he’s been stabbed in the neck”.

Police on scene at Mayfield. Picture: Nine News.

Mr O’Brien had been drinking with Johnson and another friend before the fight broke out.

His parents, who were staying with him for Christmas, had gone to bed a short time earlier.

Another neighbour, Leanne Burley, told the court she heard Mr O’Brien’s mother responding to her injured son.

“I heard a guttural moan,” Ms Burley said.

“Then I heard someone say ‘stay with us Steve, stay with us’.”

The trial before Justice Richard Cavanagh continues.