Newcastle Supreme Court judge Stephen Rothman on Wednesday said Joshua Walker Smith, 36, and the victim, Ewan Sams, 36, had been friends but their friendship was strained because of the Smith's relationship with Mr Sams' ex-girlfriend Kirby Armstrong.

The judge accepted Smith never intended to seriously harm or kill Mr Sams and was only trying to help Ms Kirby collect her belongings.

Smith, a father of two, had been due to stand trial last month for murdering Mr Sams before the NSW Director of Public Prosecutions agreed to accept his guilty plea to the lesser charge of manslaughter.

He will be eligible for parole after serving three years and eight months.

Mr Sams' mother Janelle Sams said there was no sentence that would bring Ewan back, and it was up to Smith to turn his life around to be released at the end of his non-parole period.

"He's lucky to have a second chance because he took Ewan's second chance away," she said.

Smith admitted driving his 4WD about six to seven metres straight into Mr Sams, who was wielding a metal pole, and crushing him against his garage.

Smith, with Ms Armstrong in the passenger seat, then reversed out of the gate and drove off.

Justice Rothman on Wednesday said Smith had suffered significant mental health issues because of his traumatic childhood which involved significant domestic violence and substance abuse.

On the night Mr Sams was killed, Smith and Ms Armstrong had driven to his home in Cessnock, at about 11pm on September 25, 2018, because Mr Sams was refusing to hand back her belongings.

Mr Sams claimed Ms Armstrong owed him money.

The couple crashed into the gate to access the backyard and saw Mr Sams going in and out of the house getting piles of Ms Armstrong's belongings to put on a fire.

When Ms Armstrong went to the back door, Mr Sams put her arm behind her back and held her close so she couldn't move before bending her backwards over the railing.

Ms Armstrong managed to get back to the 4WD which Smith had parked near the clothesline when Mr Sams ran at the vehicle and tried to lift her out before Smith yelled at him to leave her alone.

Smith told Mr Sams, "You're not f***ing taking her mate, stop it."

Mr Sams picked up a metal pole and told Smith, "I'm gunna kill her" and "You can f***ing have her."

Mr Sams then picked up a paver and smashed the windscreen.

After Smith unsuccessfully tried to reverse out, Mr Sams threw the paver at him.

Smith then put the 4WD in first gear and accelerated towards him, crushing him against the garage.

Mr Sams screamed "Stop!" several times after being struck.