A two-week session of hearings will begin a comprehensive inquiry into the deaths of victims Tori Johnson and Katrina Dawson during the siege, which started on the morning of December 15 last year.
Coroner Michael Barnes will also examine the death of gunman Man Haron Monis, what was known of him as a security risk and how the siege was managed by police.
'It's not time to speculate or to develop theories'
It was 2:14 in the morning on December the 16th last year, precisely 16-and-a-half hours after gunman Man Haron Monis took 10 customers and eight employees hostage.
Within hours, New South Wales Police Commissioner Andrew Scipione was cautioning the public to await the results of an investigation into what unfolded.
"We need to actually find out what's happened here and what's happened inside that cafe. It's not time to speculate or to develop theories. We're going to work through the facts, and we will advise you as soon as we can," he said.
A two-week inquest into the deaths of Monis, cafe manager Tori Johnson and a customer, Sydney barrister Katrina Dawson, is expected to provide answers.
It follows a one-day session in January that heard Ms Dawson was killed by ricocheting fragments of a police bullet or bullets after the police stormed the cafe.
That session, at the New South Wales Coroner's Court in Sydney, also heard the storming of the cafe followed the execution of Mr Johnson by Monis.
This two-week session is focusing on Monis's background.
More than a hundred witnesses and experts are expected to appear over the course of the full inquest, running over the rest of the year.
The findings are expected to be delivered early next year.
Man Haron Monis 'no stranger to Australian authorities'
Man Haron Monis first came to public attention in 2010, when he faced charges over sending offensive letters to the families of two Australian soldiers who died in Afghanistan.
At the time of the siege, Monis's former lawyer, Manny Conditsis, described him as a "damaged-goods individual".
"His ideology is just so strong and so powerful that it clouds his vision for common sense and objectiveness. Knowing that he was on bail for very serious offences, knowing that, whilst he was in custody, some terrible things happened to him, I thought that he may consider that he's got nothing to lose, hence participating in something as desperate and outrageous as this."
Monis was facing charges of being an accessory to his ex-wife's murder and on 40 offences relating to the indecent and sexual assault of several women in 2002.
Out on bail, he had been due to reappear in court in February.
Just before 9:45 on the morning of December the 15th, he made his move in the Lindt Cafe, forcing Tori Johnson to phone 000.
Monis was carrying a sports bag and armed with a shotgun.
He demanded a hostage ask all media to broadcast that it was an attack on Australia by the self-proclaimed Islamic State.
He also demanded to talk to Prime Minister Tony Abbott live on radio, a demand that was rejected.
Five of the hostages escaped out various exits in the afternoon, and, after the last ones, Monis threatened to kill others.
It was more than nine hours later before police stormed the building, setting off stun grenades, shooting Monis and bringing the siege to an end.