A young soldier's death after being shot in the head during a live-fire exercise was a catastrophic failure to comply with work health and safety duties.
Victorian soldier Private Jason Challis, 25, died after he was shot at the ADF's Mount Bundey training area, about 120 kilometres southeast of Darwin, in 2017.
He was accidentally shot in the head and knee during an urban warfare exercise in a mock town made of plywood and hessian.
Safety procedures should have protected the much-loved 5th Battalion rifleman, who had joined the ADF 10 months earlier.
But no one had noticed he'd wasn't with his team as it entered the makeshift structure and was instead crouching behind a target when two soldiers fired on it.
The Defence department has pleaded guilty in the Northern Territory Local Court to failing to comply with its health and safety duty.
The court heard "vagaries of the human factor" were a key cause of the incident, along with "inadequate compliance" to, a "deliberate disregard" for and a "momentary lapse" from procedures.
But the primary failures were that the soldier's corporal hadn't ordered the group to do a practice run before the exercise, and this wasn't picked up by commanders.
The danger zone or possible angles or arcs of fire where Pte Challis was positioned were also not properly marked.
Judge Elisabeth Armitage said the breach had put every soldier involved in the exercise at risk.
"With all of these mechanisms in place and a failure for any of them to work, it seems to point to a catastrophic failure to comply with the work health and safety duties," she said.
"The damage done to each of those people on the ground and their families is obvious, and their families."
Prosecutor Jennifer Single SC said it was a significant departure from the acceptable standard.
"What this prosecution is about is that the policies existed ... but there were no mechanisms to ensure that those policies were actually complied with," she said.
The ADF investigated nine serving members closely linked to the incident. One was sacked and six others were reprimanded.
The army has since rewritten and bolstered its safety and training procedures and is in the process of improving its training infrastructure.
It will also pay Pte Callis's family reparations and is likely to be fined. The maximum penalty is $1.5 million.
The case will return to court on June 18.