The Defence Department has admitted breaching its duty of care to a young soldier killed in a Northern Territory live-fire exercise.

Victorian soldier Private Jason Challis, 25, died after he was shot in 2017 at the Australian Defence Force’s Mount Bundey training site, about 130km southeast of Darwin.

The department pleaded guilty in the NT Local Court on Tuesday to failing to comply with its health and safety duty.

Pte Challis was shot in the head and knee during an urban operation exercise called Tigers Run in a mock town.

He and three other members of a four-soldier team entered a wood and hessian building to engage mock targets.

Two other members of his team fired at a target that Pte Challis was crouching behind.

“His head wound was immediately non-survivable,” prosecutor Jennifer Single told the court.

“He died several hours later in Darwin hospital but it was immediately non-survivable.”

The team was supposed to have moved as one to prevent the soldiers from firing on one another.

It is not known why he became separated despite investigations by the NT coroner, the ADF and the NSW police forensics unit.

“What is clear is that Private Challis did not move with the rest of the (group) to the front of the building,” Ms Single said.

“When you hear stop, stop, stop that’s when they find Private Challis,” she said in reference to a video of the exercise played to the court.

It took more than a minute to find him after the exercise was restarted due to the earlier safety breach when the supervising officer observed the team had separated.

Three ADF safety supervisors were with the team when the incident occurred.

Defence was facing three counts of failing to comply with health and safety duty after an investigation by the work, health and safety regulator Comcare.

But two charges were dropped and one amended.

The case continues.

-AAP