Prosecutors allege Sebastian Lewis Hogan, 19, acted as a vigilante when he goaded a group of young men to come to his family home in Bonython in the early hours of January 13 last year, believing they had vandalised his car the previous day.

The Crown alleges he and his father Andrew Jay Hogan, 49, armed themselves and waited in ambush outside until the group arrived.

The ACT Supreme Court trial of the pair is in its closing stages, and Crown prosecutor Sara Gul and defence barristers Steven Whybrow and Jason Moffett gave their final submissions to the jury on Monday.

Sebastian Hogan, the court heard, had become suspicious that youths involved with a group naming itself "One Life" were responsible for smashing his car's windows and leaving a boulder on its bonnet.

The Crown says the son told them to come to his Bonython home, warning them they would lose "street cred" if they didn't.

Ms Gul said he then told his father the group were coming round to bash him, and the pair went outside and waited.

It is alleged Sebastian Hogan used a baseball bat to hit one of the youths, Jake Warcaba, in the head when he arrived.

The Crown alleges Mr Warcaba was tied up, while another man, Nathan Krecak, was threatened by the gun-wielding father. Mr Krecak had also been hit in the head with the bat, tied up, and, the Crown alleges, sustained injuries when he had been dragged along the ground.

"This is not a self-defence case ... this is vigilantism," Ms Gul said.

"This is an ambush."

But Mr Whybrow, acting for Sebastian Hogan, argued his client had acted reasonably in self-defence against a threat to his safety, his father and mother's safety, and against the family property.

"Heaven help us if a group of four thugs come round to our house in the middle of the night," he told the jury.

Mr Warcaba, he said, was dressed for a fight when he appeared outside the Hogans' Bonython home at 2am.

He was wearing a hat and sunglasses, his shirt was being used to cover his face, and he walked "he-man" style up to Sebastian Hogan.

Mr Whybrow said Sebastian Hogan only delivered a "glancing blow" with the bat, which had been proportional to the threat, and only caused minor injuries which did not fit with the Crown's case.

The use of the cable ties, Mr Whybrow argued, was either in self-defence or lawfully as part of a citizen's arrest.

Mr Moffett said his client, Andrew Hogan, had not armed himself with the gun or cable ties until he realised the group were about to beat his son to a pulp.

The gun was unloaded and was not used to "butt-whip" the youths, he said.

The Crown has highlighted the fact that the pair did not call police before the group's arrival, despite knowing they could be coming.

The police were called after Mr Warcaba was restrained, but before the second youth, Mr Krecak, was tied up.

Justice John Burns is expected to deliver his summing up to the jury on Tuesday.