A former Defence chief says the killing of an unarmed man by a Special Air Service (SAS) soldier in an Afghan wheat field "would be a simple case of murder" if it happened on Australian streets.

Key points: An expert in war crimes says the soldier could face an Australian court for the killing

An expert in war crimes says the soldier could face an Australian court for the killing The Inspector-General of the Australian Defence Force is currently investigating the conduct of special forces in Afghanistan

The Inspector-General of the Australian Defence Force is currently investigating the conduct of special forces in Afghanistan Federal MP Andrew Hastie has described the footage of an Afghan man being killed by an Australian soldier as "morally repugnant"

Retired Admiral Chris Barrie, who served as chief of the Defence Force from 1998 to 2002, was "shocked" at footage on Monday's Four Corners program that showed an Australian special forces soldier killing an unarmed Afghan man in May 2012.

A Defence investigation of the incident found the soldier acted in self-defence.

Mr Barrie said he could only comment on what he saw watching the program.

"The man was not armed, the man was in a docile situation, and he was shot," Mr Barrie said.

"Which, if this was to happen on the streets in Australia, would be a simple case of murder.

"Now, in a situation where you have armed forces which are carrying out tasks in another place, under the appropriate rules of engagement and the laws of armed conflict, this is a war crime."

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 2 minutes 12 seconds 2 m 12 s GRAPHIC CONTENT WARNING: Video which shows a Special Air Service (SAS) operator shooting an unarmed Afghan man.

'I felt ashamed': Hastie

Federal MP and former SAS soldier Andrew Hastie said he found the footage "morally repugnant".

"Like any normal Australian, I had that visceral reaction, but also as a former Australian soldier myself who wore our flag on my left shoulder overseas on operations, I felt ashamed and many Australians probably feel the same way," Mr Hastie said.

Liberal MP Andrew Hastie was an SAS captain before becoming a politician. ( Jed Cooper )

The soldiers involved in some of the incidents shown on Four Corners "need to be stood down immediately" said the Australian Director of Human Rights Watch Elaine Pearson.

"If someone committed a crime like that on video on the street in Sydney, you wouldn't expect that person still to be walking around years later," Ms Pearson said."

The soldier, who the program called Soldier C, told a Defence investigation of the incident that the young man, Dad Mohammad, had been seen with a radio.

Soldier C also said he shot Dad Mohammad from 15 to 20 metres away.

However, the footage shows him shooting the young man at close range while the man lies still with no weapon or radio apparent.

Soldier C was cleared during an ADF investigation of the incident, which found that he had acted in self-defence.

He is still serving in the ADF.

Soldier could be prosecuted in Australian criminal courts

Stephen Rapp is an expert in war crime prosecutions and served as the chief prosecutor in the Sierra Leonne special court and the US ambassador-at-large for war crime issues under former US president Barack Obama.

Mr Rapp watched the wheat field killing vision in the Four Corners program and said there was a "strong and indictable" case for murder as a war crime.

"Once a person is out of combat and unarmed and not able to do you damage or contact anyone that can do you damage, then they are a victim that you cannot shoot any more than you can shoot you or me, if you were laying on the ground in your home country in front of our own homes," Mr Rapp said.

He said the soldier could be prosecuted in Australia for an alleged war crime committed in Afghanistan.

Chris Barrie served as the Chief of the Defence Force from 1998 to 2002. ( AAP: Alan Porritt )

The case would only end up in the International Criminal Court if the Australian authorities failed to carry out proper investigations and trials, Mr Barrie said.

"I think [Australian soldiers] should be dealt with in Australian law," the former Defence chief said.

"And I think our laws are pretty solid when it comes to war crimes."

After the program aired, the ABC sent questions to the Department of Defence about whether Soldier C would continue to serve in the armed forces.

A spokesperson said the ADF was waiting on the findings of the ongoing Inspector-General of the Australian Defence Force's (IGADF) inquiry into the conduct of Australian Special Operations in Afghanistan.

"Defence is extremely concerned by the matters raised in the 4 Corners program on Monday night," a Defence spokesperson said.

"Following receipt of the IGADF's Afghanistan Inquiry report and consideration of its findings and recommendations, the CDF (Chief of the Defence Force) will decide what action should be taken."

Mr Rapp said the soldier who shot the Afghan man in the video should be removed from active duty during any investigation.

"When it comes into the hands of the chief of the Defence Force, he should proceed to do what he can to make sure this matter is completely investigated and given the evidence that we've seen here, prosecuted in the appropriate courts."

Mr Hastie said he had faith in the IGADF process.

"I have confidence that the Government, the Minister for Defence, CDF and everyone in the chain of command is doing their job," he said.

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'He showed moral courage'

Samantha Crompvoets, whose confidential report for Defence kickstarted the IGADF's inquiry, was "disturbed' by the field footage.

"Not only does it depict what looks to be unlawful killing, it also illustrates how uneasy some of the soldiers felt about what they were witnessing or a part of," Dr Crompvoets said.

"Any soldier involved in unlawful killing should be stood down, yes.

"It illustrates that there were significant issues and unlawful behaviours that had become normalised, and at worst, were being celebrated.

"Sadly, it renders invisible the many outstanding and professional special forces soldiers who have only ever conducted themselves with integrity."

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Mr Barrie has criticised the number of times Australian soldiers had been forced by their leaders to deploy to Afghanistan.

Braden Chapman served with the SAS in Afghanistan as a signals intelligence officer. ( Supplied )

"I think the all-volunteer force with successive deployments has lost its moral compass," Mr Barrie said.

"Those folks have been going back and back and back [to Afghanistan] and I think that has contributed a lot to what we saw [on Four Corners]."

Braden Chapman, a former SAS signals intelligence officer, blew the whistle on what he witnessed in Afghanistan.

Former servicemen Mr Barrie and Mr Hastie commended Mr Chapman for speaking out about his colleagues' actions in Afghanistan.

"I think he did something that was very brave," Mr Barrie said.

"He showed moral courage and he should be commended for what he did," Mr Hastie said.

"The Australian people should be thankful that we have people like him who are willing to stand for truth and for justice."