Vic man killed stepson in 'self-defence'

A Melbourne man was acting in self-defence when he stabbed to death his drunk, armed and abusive stepson, his barrister says.

John Adams thrust a knife into the heart of his stepson, Joel McDonald, outside his Brunswick East home during a heated argument.

Police arrived to find Mr McDonald dead in the gutter and Adams confessing to the killing.

Adams, 55, is charged with murder.

Defence barrister, David Hallowes, said Adams had killed Mr McDonald, but had acted to defend himself against the enraged man who had brought a knife and baseball bat to confront him.

"When John Adams struck Joel McDonald with the knife on a number of occasions he was acting in self defence," Mr Hallowes told the Victorian Supreme Court.

"It was Joel McDonald who bought the knife around and it was Joel McDonald who initiated the contact."

Adams told police at the scene, "He was going to beat the s*** out of me", Mr Hallowes told Adams' trial.

The jury heard Mr McDonald, 38, was aged just eight when Adams effectively became his substitute father following the death of his biological dad.

Adams has since been in a 34-year relationship with Mr McDonald's mother, Cheryl McDonald.

"He (Mr McDonald) was raised as his son," Mr Hallowes told the jury.

The couple also played a significant role in the life of Mr McDonald's 11-year-old daughter when he had custody of her on weekends.

But prosecutor Mark Rochford said it was a disagreement over his daughter which began the chain of events that led to Mr McDonald's death on May 4, 2013.

The court heard that Mr McDonald flew into a rage when he learned his mother picked up his daughter from his Keilor home without permission.

Mr Rochford said he then asked his partner for cash to buy a gun.

When she refused he demanded she drive him to the home of his mother and Adams.

Witnesses reported seeing two men arguing and grappling with one another on the road outside Adams' house, Mr Rochford said.

He told the jury they would hear evidence about Mr McDonald's excessive alcohol and drug use and his aggressive nature.

"You probably won't think he's a very attractive person," he said.

But he said Adams did not truly believe he had to stab Mr McDonald to protect himself.

A pathologist found Mr McDonald had a .24 per cent blood alcohol level and traces of cannabis in his system when he died.

The trial continues.