It was not an act of self-defence as the defence has suggested, crown prosecutor John Dickie told the Geelong Supreme Court jury on Thursday.

Instead, Haig knew his decision to fire the gun would result in the death or serious injury of his 31-year-old brother David.

"This wasn't just a gun going off and an accidental discharge. There were two shots fired," Mr Dickie said in his closing address.

"That's not intending to scare someone. It's not intending to just hurt someone."

Haig, then 39, does not deny shooting his brother at their Geelong home on October 5, 2020, but he denies the charge of murder.

His lawyers have argued it was an act of self-defence because Haig was threatened and scared of his brother.

The jury was that told in the weeks before the shooting, David had grabbed his older but smaller brother Haig around the throat and strangled him.

Mr Dickie conceded David was a "flawed human being" but he also "wasn't a monster".

"He was no Michael Myers figure hell bent on killing or seriously injuring Haig," the prosecutor said, referring to the fictional character in the Halloween film series.

"He wasn't out to get Haig and that was not how he perceived him."

The prosecutor's closing arguments are expected to continue on Friday, before the defence lawyer Jarrod Williams begins his final address.

Australian Associated Press