'Lone wolf' Australian hostage-taker had violent, unsettled past

DEEP SCARS

He compared himself to Wikileaks founder Julian Assange, saying he was being persecuted for his political beliefs.

"Since the Australian government cannot tolerate Sheikh Haron's activity, (it) is trying to damage his image by these false accusations," he wrote.

While in prison Monis claims he was tortured, smeared with excrement and forced to sleep on a bare concrete floor, Conditsis said.

"I know that left quite deep scars for him," he said.

"If he had formed the view prior to this siege that he was going to inevitably go back to prison, whether he was guilty or not ... I can see that might have unhinged him."

Despite the warning signs, police must focus limited resources on groups attempting to pull off major terrorist attacks, said Greg Barton, director of the Global Terrorism Research Centre at Monash University in Melbourne.

There are only a tiny category of people at any given time police can legally and financially justify keeping under surveillance and Monis did not qualify, he said.

"On the triage priority list, he would be well down that list," Barton said.

"I don't think it's a case of a failure or a mistake. I just think it's a case of the harsh reality of dealing with this kind of threat."