The video screened on Four Corners on Monday night could result in charges of war crimes, the ABC program reported.

The footage of a Special Air Services Regiment raid on a village in Oruzgan province in May 2012 shows a man cowering in a wheat field as an SAS soldier stands over him and shoots.

The disturbing combat vision has emerged as the Inspector-General of the Australian Defence Force examines 55 separate incidents involving Australian special forces deployed to Afghanistan, including allegations of unlawful killings of non-combatants.

The video, taken by the helmet camera of a dog handler, records members of the 3 Squadron SAS patrol disembarking from one of two Black Hawk helicopters looking for an insurgent bombmaker.

Four Corners reported that the bearded man in the wheat field appeared to be carrying red prayer beads when the patrol scout fired three shots into his head and chest from between one and two metres away.

The dead man was named as Dad Mohammad, who was thought to be 25 or 26 years old.

The gruesome video is at odds with what soldiers told Australian Defence Force (ADF) investigators, who later ruled the killing was justified because it was in self-defence.

A former soldier who served with the same SAS squadron described the vision as looking like a "straight-up execution".

Braden Chapman, a signals intelligence officer, was not a witness to the killing but served with 3 Squadron SAS on the 2012 Afghanistan deployment.

"He's asked someone of a superior rank what he should do, but it comes down to the soldier pulling the trigger," Mr Chapman said. "It's a straight-up execution."

Mr Chapman was shocked by what he saw on the video.

"That soldier there is not someone I saw do anything like that, and he didn't usually act like that either," he said.

The wheat field shooting was one of several cases Four Corners said may constitute war crimes.

Initial ADF investigations ruled that Dad Mohammad was lawfully killed because he posed a direct threat to the Australians.

Defence did not answer questions from Four Corners about his killing and other allegations of war crimes.

In a statement the ADF said the Inspector-General's inquiry into "whether there is any substance to rumour and allegations" about possible war crimes was ongoing.

Four Corners said the SAS soldier who killed Dad Mohammad was still serving in the special forces.

Mr Chapman told the ABC program that he had witnessed a separate incident involving another SAS soldier, also still serving, who allegedly shot an Afghan man twice in the chest and once in the head after the man had thrown away his phone and raised his hands.

When another patrol's assault dog was allowed to chew on the dead man's head, the animal's handler said "Let him have a taste", Mr Chapman alleged.

Acknowledging that he feared possible retribution for speaking out, Mr Chapman said: "I just want the truth to come out and people who did commit crimes, be held accountable."