Vic autistic teen's killer gets 24 years

A Victorian man who told a 14-year-old autistic boy to die as he murdered him with an axe has been jailed for 24 years.

Joel Parker Henderson, 42, killed Timothy O'Brien, known as Timmy, despite the pleas of a woman at the scene to spare his life in what a judge says was apparent "retaliation" for the young man's defence of his stepfather.

Henderson's co-accused, Darren Wilson, 37, is serving a 30-year sentence for the horrific crime.

The night of the murder, January 5, 2013, Henderson and Wilson had planned to ambush Timmy's stepfather, Peter Williams, at a house in Scarsdale, near Ballarat.

A woman named Rachel Curtis lured Mr Williams over to a share house saying she thought she had heard a prowler.

Timmy, who had a close relationship with his stepfather and followed him everywhere, insisted upon going along, armed with a torch and a baseball bat.

When they arrived, Wilson attacked Mr Williams, leaping out of a bedroom and punching him in the face until he bled.

Timmy tried to protect his stepfather, striking Wilson with his baseball bat until he fell to the ground.

Armed with an axe and a "vicious" looking knife, Henderson entered the house.

Seeing the axe, Timmy started hitting Henderson with the bat.

Henderson struck Timmy with the axe.

A woman who was there shouted, "Leave him alone, he's only a little boy. He has special needs."

"You persisted," Justice Bernard Bongiorno said, in sentencing Henderson on Friday.

Henderson said "die, c***, die" as he hit the boy.

Wilson then took the weapon and attacked Timmy.

"You did nothing to stop him," Justice Bongiorno said.

Timmy died where he lay from horrific injuries inflicted by the pair.

During a pre-sentence hearing, Henderson's defence barrister said his moral culpability should be reduced because he has an acquired brain injury.

However it was not suggested at trial that he didn't know what he was doing.

Justice Bongiorno said other factors, such as community protection, also had to be taken into consideration.

"Timmy's mother and sister both miss him," Justice Bongiorno said.

"Timmy's stepfather misses him as a companion and workmate."

Henderson was ordered to serve at least 20 years before being eligible for parole.