A man accused of lighting a fire that killed three people at his inner western Sydney shop in 2014 has claimed he was tied up and robbed by armed men on the night of the blaze, a court has heard.

Adeel Khan is charged with murdering Chris Noble, as well as Bianka O'Brien and her baby son Jude, who lived in separate units above his Rozelle convenience store.

Khan has pleaded not guilty to the charges.

Defence barrister Luke Brasch told the New South Wales Supreme Court the accused had "no control" over that night's events because armed men, "people with criminal intent", robbed, threatened and held his client against his will.

On Monday, prosecutors said Khan had placed up to 10 plastic containers of fuel around the shop and laid fuel-soaked cloth trails between them.

Today the defence said it was the men who had robbed Khan who set up the containers.

"Most of the time Mr Khan was tied up, or his eyes were covered," Mr Brasch told the court.

Mr Brasch denied his client was experiencing serious financial stress that could serve as a motive for lighting the blaze.

"He was a family man, a small businessman, father of three children ... he was travelling along fine," Mr Brasch told the court.

Bianka O'Brien and her 12-month-old son Jude were among three people killed in the blast. ( Facebook )

"On behalf of Mr Khan, he denies that he is culpable for the tragic events of 4 September 2014 ... Three innocent people including a young child lost their lives."

The husband of Bianka O'Brien, John O'Brien, said Khan knew his young family lived upstairs and that the shop owner would often enquire about his son.

"It was just a friendly, neighbourly relationship," Mr O'Brien told the court.

Corey Cameron, a resident of the building, told the trial "the whole place seemed to be caving in" when he escaped.

The resident said when he discovered Mr Noble had not escaped, he tried to jump back onto his balcony, and called out to his friend.

"I heard him screaming back for a bit...[Mr Noble said:] f***, f***!" Mr Cameron said.

Shop owner said he was sorry after fire

Earlier, in his opening address, crown prosecutor Mark Tedeschi QC told the court Khan became trapped in the rubble after an explosion and told an ambulance officer he was "sorry".

Mr Tedeschi said the blaze was so fierce, firefighters were unable to immediately extinguish it.

Firefighters ran to the rear of the Darling Street building and "one of them saw the accused's hand poking out and they heard him calling out".

Bianka's husband John O'Brien said Khan knew his young family lived upstairs. ( AAP: Dan Himbrechts )

Mr Tedeschi said the blast was so powerful the accused became trapped underneath a fridge in the debris and "he required five burly firefighters to lift that fridge off him".

The court heard ambulance officer Amy Gardiner asked the accused if he knew where he was, to establish his level of consciousness.

"I'm so sorry. I'm so sorry. I didn't mean it. I'm so sorry," Khan allegedly replied.

The court was told that Ms Gardiner said to Khan: "I don't care what you've done or what you're sorry for. You need to shut the f*** up, answer my questions and do as I say."

The crown prosecutor said when Khan was taken to hospital, a carbon-fibre breathing mask was found in his trousers, and his jeans, shirt, jacket, belt and shoes tested positive for petrol.

The court was also told a red container was found in the boot of the accused's car containing 10 litres of petrol.

The convenience store owner set fire to the store because he wanted to get out of a five-year lease on his failing business, the court heard on Monday.

The case continues.