An international expert says the Sydney Lindt cafe siege was "overwhelmingly" an act of terrorism and gunman Man Haron Monis was a terrorist.
Professor Bruce Hoffman, is the director of the Centre for Security Studies at Georgetown University in the United States who has worked with the CIA and advised on counter-terrorism issues in Iraq.
Prof Hoffman told the inquest into the siege on Tuesday it didn't matter whether Monis had direct contact with Islamic State because he was "inspired, motivated and ultimately animated" by the terrorist group to carry out the attack.
Prof Hoffman, who spoke via videolink from the US, said he followed the siege in the news as it unfolded last December 15 and 16, and believed at the time it was a terrorist attack.
After the tragedy he looked at Monis's online rantings, including his website postings where he pledged allegiance to the Islamic State.
"In this expert's view the case is overwhelmingly that it was terrorism," Prof Hoffman said.
His analysis is at odds with two Australian terrorism experts who told the inquest it wasn't a terrorist act.
Associate Professor Rodger Shanahan from the Australian National University, said Monis was a person with mental health issues acting on a personal grudge.
Prof Hoffman said Monis had "a long trajectory of radicalisation" and his mental health issues - delusions of grandeur, narcissism and a lack of empathy - made no difference in assessing him as a terrorist.
"A terrorist can be someone who has proven mental health disorders," Professor Hoffman said.
Theodore Kaczynski, the so-called "Unabomber" who carried out multiple attacks in the US between 1978 and 1995, displayed mental illnesses but was considered a terrorist, he said.
Monis stated political rather than personal aims, did not seek money or personal reward for his crimes and claimed he was acting for Islamic State, Professor Hoffman said.
"The violence didn't come out of the blue but rather, in the perpetrator's mind, was in the service of this organisation," he said.
Monis was at great pains to state his allegiance to Islamic State during the siege, Professor Hoffman said, which fitted with the kind of "lone wolf" terrorist attack encouraged by the group.
Reports that Monis allowed his hostages toilet breaks and food are also irrelevant, Professor Hoffman said, as he continued to hold them at gunpoint.
"I still have confidence in characterising him as a radicalised terrorist," Professor Hoffman said.
A panel of terrorism experts will give evidence on Wednesday.
