Fredon Laith Botrus, 20, has pleaded not guilty to murdering Alfredo Isho, who was knifed while seated and gowned at Bossley Park's Classico Hair Studio on January 11, 2019.

During a two-week NSW Supreme Court trial, witnesses told the jury of seeing a helmet-wearing assailant enter the rear of the shop and plunge a knife into Mr Isho's chest.

During his summing-up on Wednesday, Justice Michael Walton noted a submission made by the defence barrister who referred to two girls in the public gallery having "acted inappropriately" during the playing of the police interview with Botrus.

The barrister emphasised Botrus should not be judged by them, while the judge reminded the jurors any reactions to the playing of the interview played no part in the trial evidence they had to consider.

The evidence has included the discovery of a white motorcycle in the Botrus family home, where it was found stripped of parts in the garage.

The Crown alleged the location of the bike, the finding of Mr Isho's blood on the jumper Botrus was wearing when arrested 150 minutes after the stabbing and encrypted messages on his phone show he was the killer.

But his barrister urged jurors to consider how the circumstances in which police came to observe Botrus in the jumper were "consistent with him playing a role other than that of him being the murderer".

Gaps in CCTV coverage meant the true killer had "every opportunity" to dump the bike in the Botrus family's garage, strip it of parts and escape, he said.

Justice Walton is continuing his summing-up before the jurors retire to consider their verdict.

Australian Associated Press