A coronial inquest into the deaths of three soldiers shot by an Afghan National Army sergeant in 2012 has heard they weren’t properly guarded.

Australian soldiers on a mentoring mission in Afghanistan that turned deadly didn’t properly guard themselves against an insider attack, an inquest has heard.

A coronial inquest into the deaths of three soldiers shot by a rogue Afghan National Army sergeant in 2012 entered its fourth day on Friday.

Lance Corporal Stjepan Milosevic, Sapper James Martin and Private Robert Poate were gunned down at a patrol base 20km north of Tarin Kowt in Oruzgan province on August 29, 2012.

The Brisbane inquest has so far heard only one roaming sentry, known as a “picquet”, was guarding the 24-man Australian camp at patrol base Wahab on the night of the attack.

Afghan soldiers were mingling with Australian troops when the rogue soldier, named Hekmatullah, approached a group of diggers playing cards and opened fire with an automatic weapon from a range of five metres.

On Friday the task force’s commanding officer, who was stationed elsewhere at the time, confirmed that in August 2012, all interactions between Afghan and Australian soldiers were supposed to be closely watched over by a guard, known in the army as a “guardian angel”.

Major Travis Gordon said the threat of an insider attack had been a continuing focus following the deaths of three Australians at a different patrol base less than a year earlier.

Counsel assisting the coroner Anthony Marinac asked if the Australian soldiers who were socialising with the Afghans at the base would have required a guardian angel watching over them.

“Yes,” Maj Gordon replied.

“So a roving picquet who’s moving up and down the general area and who’s not specifically focused on that area wouldn’t satisfy that requirement?” Dr Marinac said.

“No,” Maj Gordon answered.

The inquest has heard evidence the platoon’s commander was unaware of the requirement for a guardian angel and that the platoon didn’t have enough men to guard itself from an insider attack.

The Brisbane inquest is being held at the request of the dead soldiers’ families, who were in court on Friday.

Hekmatullah has close ties with the Taliban and has been sentenced to death for the murders.

The inquest will continue on Monday.