Former police officer Michael Schultz, who was among the first on the scene, told the Supreme Court on Tuesday how he and others forced their way into the room and first encountered lawyer Peter Wallis looking "charred and black".

They helped him out and soon after heard moaning coming from a corner.

Mr Schultz said there was "lots of mess" with desktops, ceiling panels and office furniture piled up, but when they removed some of the debris they found Detective Sergeant Geoffrey Bowen.

"I could only see him from the back. All I observed and could hear was this intermittent low moaning sound," he told the court.

"From my perspective, I was hoping he was alive and I was trying to talk to him and reassure him and encourage him to hang in there."

Mr Schultz said as they turned Sgt Bowen, he saw that his left arm was missing from beneath the elbow and that his left trouser leg was shredded with bits of flesh showing through.

Sgt Bowen died from his injuries while Mr Wallis lost an eye and was severely burnt.

In other evidence on Tuesday, another NCA worker at the time told of the assistance she offered Mr Wallis immediately after the blast.

She said he was burnt from the waist up and his face was unrecognisable.

"You wouldn't have known it was Peter except for the sound of his voice," Joanne Taskas said.

Domenic Perre, 63, has gone on trial over the attack but has pleaded not guilty to charges of murder and attempted murder.

His defence team previously told the court he was "explicit" in proclaiming his innocence both immediately after the bombing and in relation to the charges he currently faced.

The prosecution has alleged the bombing of the NCA office was a personal attack on Sgt Bowen,

In the Crown's summary of the case against Perre, Sandi McDonald SC detailed the "multi-layered body of circumstantial evidence" against the 63-year-old.

She said Perre's hostility towards detective Bowen had grown because of their interactions following the seizure of a multi-million-dollar cannabis crop in the Northern Territory in August 1993.

While a number of people had been arrested, Perre was also suspected of being involved and was targeted by police and Sgt Bowen, who had been seconded to the NCA.

"It is the prosecution case that it was no accident that Geoffrey Bowen died as a result of this bomb detonating. He was the intended target," the prosecutor said in her 60-page opening.

"The bomber intended that the parcel bomb travel through Australia Post and end up in the hands of Bowen and that when he opened it his body would suffer the full force of the explosion."

The trial is continuing before Justice Kevin Nicholson who is presiding over the case in the absence of a jury.

Australian Associated Press