New South Wales state Coroner Michael Barnes told the inquest on Monday that getting to the bottom of what caused 50-year-old Man Haron Monis to take 18 people hostage at a Sydney café late last year was a matter of national importance.

"Was Monis a so-called lone wolf prosecuting an ISIS-inspired (Islamic State) terrorist act, or was he a deranged individual pursuing some personal, private grievance in a public manner? They are real questions we must try and answer if an explanation for the siege is to be forthcoming and strategies to avoid a repeat are to be developed," Barnes said.

Lawyers assisting the inquest painted a picture of Monis as a narcissist who was "prone to grandiose claims."

"His constant goal in life appears to have been achieving significance," one of the lawyers, Sophie Callan, said.

She added that Monis was "almost entirely consumed in his own self-importance and when challenged, his self-control would occasionally slip and his reaction was disproportionate."

She also said that in 2012 or 2013 Monis had attempted to join the Rebels Motorcycle Club, but that the notorious biker gang found him to be too "weird."

"Ultimately, he was rejected by the Rebels and they took his motorbike," she said.

'Modest' mental illness

Another lawyer, Jeremy Gormly said that while Monis did have a history of mental illness, this was not severe.

"Mr. Monis, as we shall see, unquestionably had at stages in his life some mental health issues, but I say at the outset that any such issues appear to be modest," Gormly said. "Mental illness may not provide a full answer to the questions about his motivations for the siege."

Iranian-born Monis, had moved to Australia in 1996, where he convinced the authorities that he had been subject to persecution in his homeland. He held a number of jobs, including working as a carpet salesman and a security guard, before setting up a spiritual healing practice.

In 2014, Monis was charged with 43 counts of aggravated and indecent assault allegedly committed while working as a spiritual healer between 2002 and 2010. He was on bail on those charges as well as one of accessory to murder in connection with the death of his ex-wife when he launched the assault on the café.

Monis who claimed to be a sympathizer of the Islamic State militant group, was shot dead by police who moved into the Lindt Chocolate Café in downtown Sydney in the early hours of last December 16. Police took the decision to storm the café after Monis had shot dead one of his 18 hostages. The inquest, being held in a Sydney court room was previously told that a second hostage was killed by a ricochet from a shot fired by police.

pfd/ng (Reuters, AP, dpa)