The man who supplied the gun used to shoot police accountant Curtis Cheng dead in 2015 has given an Islamic State salute after being sentenced to 44 years in prison.

Key points: This is the first time in Australia someone has been sentenced for the offence of committing a terrorist act

This is the first time in Australia someone has been sentenced for the offence of committing a terrorist act Alou refused to stand for Justice Peter Johnson during the hearing

Alou refused to stand for Justice Peter Johnson during the hearing He will be eligible for parole in 2048, when he is aged in his 50s

Raban Alou shouted "this is only the beginning" as he was led from the NSW Supreme Court in Paramatta.

Alou pleaded guilty to aiding, abetting, counselling or procuring a terrorist act.

The 20-year-old admitted obtaining and giving a handgun to 15-year-old Fahad Mohammad at the Parramatta Mosque.

The teenager then used the Smith & Wesson .38 revolver to shoot Mr Cheng outside Parramatta police headquarters in October 2015, before being shot dead by two special constables.

Following Alou's outburst, Justice Peter Johnson commented the behaviour reinforced Alou's "almost hopeless prospect of rehabilitation".

During his sentencing remarks earlier, Justice Johnson said Alou had shown no contrition or remorse throughout the entire proceedings.

"The offender's response is devoid of basic humanity," he said.

Justice Johnson told the court this was the first time an offence of committing a terrorist act had come before a sentencing court in Australia.

Curtis Cheng, (L), pictured with his family, was shot dead outside the police complex. ( Supplied: NSW Police )

He added while there had been people sentenced for conspiracy, planning and possessing documents connected to terror, there had not been a case involving the death of another person.

"The offender was a very active planner and participant in this offence," Justice Johnson said.

"Unless the offender had obtained the firearm and supplied it to Fahad Mohammad, this crime would not have been committed.

"I am satisfied that the offender was a key person who played a lead role in the criminal enterprise."

Alou did not stand when Justice Johnson came on and off the bench.

He will be eligible for parole in 2048.

Assistant Commissioner Mick Willing said police were working to stop other people like Alou.

"We are working hard every day to prevent terrorist attacks, the threat remains at probable and we continue to work with our partners both interstate, nationally and internationally to deal with the threat," he said.

"The judge made comment again in regards to an evil ideology that was driving this person, it exists it's out there...but it will be dealt with by the courts and we'll do everything we can to ensure that the courts deal with these people appropriately."

Family praised for 'strength and dignity'

Mr Cheng's wife Selina and son Alpha were in court to see the sentence handed down.

Outside the court, Alpha Cheng said the family was satisfied with the result.

"We really hope it sets a really strong precedent that actions like this of hate and intolerance is really clearly not respected or condoned," he said.

"It sends a clear deterring factor for anyone who is contemplating such disgusting acts.

"We hope things we have to go through as a family never happens to anyone in Australia."

Justice Johnson remarked on the strength and dignity of the Cheng family in response to such an act.

Alpha Cheng said he was touched to receive those comments.

"That's how we choose to hold ourselves, with as much strength and courage through this really difficult process," he said.

"We can never remove what is happening or has happened … we will move on, we're just relieved this process is over."