Sydney siege: Gunman Man Haron Monis would have been in custody if Bail Act changes had been in place, NSW Attorney-General says

The gunman from the siege in Sydney would have already been in custody if the Government's changes to the Bail Act were in place, New South Wales Attorney-General Brad Hazzard says.

Mr Hazzard also expressed frustration at the length of time it has taken for the changes to come into force.

The comments come after more details emerge about gunman Man Haron Monis, who was no stranger to the courts.

Monis was first charged in 2009 for sending letters to the families of Australian soldiers who died in Afghanistan, labelling them murderers.

He was also charged in October last year for being an accessory to the murder of his ex-wife Noleen Hayson Pal, who was stabbed and set alight in western Sydney.

He was released on bail in December.

Monis was briefly represented by Sydney lawyer Chris Murphy, who distanced himself from the man on Twitter on Tuesday.

"In 2009, no-one could have foreseen the path that Haron Monis followed," Mr Murphy said.

"In 2009, he was a political advocate spruiking peace.

"It is a tragedy beyond belief that has brought his name back into my life."

Mr Hazzard said if tough changes to the New South Wales Bail Act were in force, that would not have happened.

"This government changed the Bail Act to ensure greater safety for our community," he said.

"It was changed to ensure that offenders involved in serious crime will not get bail. That's our intent.

"This offender was granted bail under a previous legislation, in fact under two previous bail acts."

Changes to Bail Act 'urgent'

From January 28, an accused will have to prove that they are not a risk to the community.

The Government is treading carefully after previous changes to the Act led to a series of controversial bail decisions.

However, over 40,000 people have signed an online petition calling for the changes to be enforced now.

It was created Tuesday morning by social justice campaigner Dr Miriam Giugni, who said the changes were "urgent".

"When we come down to the nuts and bolts, the Attorney-General has said that the laws coming in may have made a difference to this scenario," she said.

"I guess I'd be inclined to agree, that if there wasn't a person who was dangerous to the community around, then these things couldn't happen.

"Them coming in next year is a flag that something's happening, but this happened [on Monday].

"It's urgent that these things don't happen again."

Mr Hazzard said although it was frustrating, there was no way the Government could bring the date forward.

"It's very frustrating for us, it's frustrating for me as Attorney-General, it's frustrating for the Premier, it's frustrating for the entire Government, it's frustrating for the entire New South Wales community," he said.

"But we must actually accept the advice of our professionals ... [who] are absolutely adamant that the 28th of January is the earliest possible operational date for the new legislation."

Mr Hazzard questioned why Monis was on bail at all.

"We are asking state agencies and federal agencies to look very closely at how this offender slipped through the cracks," he said.

"How did this offender not come to the attention of state and federal agencies for more urgent action?

"We are very much at the start of that process, but early indications indicate that there are some aspects that we want pursued, and we intend to get them pursued."

However, former New South Wales director of public prosecutions Nicholas Cowdery said he was not convinced the new Bail Act would have changed the course of events.

"There will always be, unfortunately, some exceptional events which laws and controls put in place before the event could not have prevented," he said.

"I think this is one of those cases.

"We just need, unfortunately, to deal with it, and of course take all the steps that we can to prevent anything like this happening in the future by people being much more alert, and by ordinary members of the community being much more alert to what is going on around them and what people are doing around them."