Three men are standing trial in Melbourne over the shooting for former NSW policeman Said "Sid" Morgan in Point Cook in 2019.

He stood trial himself for murder in NSW in the 1990s after shooting his brother-in-law six times in the head.

Mr Morgan was acquitted of the crime, but boasted about it before he was shot.

Prosecutor Patrick Bourke told Supreme Court jurors in closing arguments on Thursday that it wasn't for them to decide if Mr Morgan had "got his right whack".

Irish nationals Stephen Tahaney, Mark Dixon and Jack Harvey are all charged with the attempted murder of Mr Morgan.

It's admitted that Tahaney pulled the trigger - he says in self-defence. Dixon and Harvey are alleged to have been party to an agreement to harm Mr Morgan, knowing it was probable he would be killed.

Mr Bourke said there was no doubt Mr Morgan was the catalyst for events leading to him being shot with his own gun.

He had been called for help by his longtime friend Daniel Saddik, whose business dealings with Tahaney and with Dixon's brother had soured.

In text messages Mr Morgan had told Tahaney to kiss his family goodbye and said that "like anything, it gets easier the second time around".

Mr Bourke said Mr Morgan was the type of person who shoots first and asks questions later, but cautioned the jury against considering karma.

"That conduct (was) barbaric. Short and simple. Sid Morgan was a copper when he did that. It's not how we operate," he said.

But he also urged the jury not to ignore Mr Morgan's past and reputation either.

"What we're engaging here in this trial is not whether Sid Morgan got his right whack, but it's whether or not the three accused men committed a very serious violent offence," he said.

CCTV footage played in the trial showed three men driving toward Mr Saddik's house, where they're approached by Mr Morgan.

Witnesses reported seeing a man being assaulted with a hammer, and two men punching and kicking another man.

A witness saw one of the men go back to the car, point a gun out the window and fire a single shot, which struck Mr Morgan in the head.

Dixon's barrister Geoffrey Steward said prosecutors want the jurors to find his client had a "cathartic development of aggression" and if he truly was scared of Mr Morgan he wouldn't have gone to the house.

But Mr Steward said Mr Morgan was there with his family friends and children.

"You might think good old family oriented Sid might draw the line to shooting you in front of youths and friends," he said.

Closing arguments are continuing.

Australian Associated Press