Anthony Caristo, 54, died after police attended his home after neighbours reported hearing a man screaming for an extended period of time.

When officers arrived, they found the front windows of his home smashed and he was lying inside in a pool of his own blood.

The officers reported blood had been smeared all over the walls and floor, Mr Caristo was holding a large knife and his left little finger was severed.

Council assisting the coroner, Ken Archer, told the court as the officers had been attempting to arrest Mr Caristo, his death must be treated as a death in custody.

He said the inquest was to determine whether the quality of care, treatment and supervision Mr Caristo received by ACT police in any way led to the cause of his death.

Mr Archer said the investigation into Mr Caristo's death had been conducted by a special team that reported to the coroner, rather than the AFP hierarchy.

"The community can be satisfied the events surrounding Mr Caristo's death was investigated competently, objectively and dispassionately," Mr Archer said.

The court heard police held serious concerns over Mr Caristo's well-being due to the blood loss and evidence he had taken drugs, as syringes had been visible on the floor.

The officers reported Mr Caristo had been rambling incoherently and in one recorded interview a police officer said Mr Caristo was "making a snow angel" in his own blood.

Videos of the officers re-enacting the scene and the body camera that began recording once the Taser was deployed were shown to the court.

Members of Mr Caristo's family left the courtroom when images of his bloodied body were shown.

Acting Sergeant Nathan Macklin use the Taser after he was unable to get Mr Caristo to drop or throw away the knife.

"I just wanted him to drop the knife so we could get in there to help him," Acting Sergeant Macklin said in a recorded interview after the fact.

"If we stood there and had done nothing he would have died on the floor. I'm certain of that."

Acting Sergeant Macklin said he witnessed Mr Caristo take the knife and slice into his own thigh twice and it had been at that point he had decided to use the Taser.

"It's the perfect scenario to use a Taser, when someone is hurting themselves with a knife," he said.

He said capsicum spray had not been appropriate as it would have filled the room with the chemical and a baton would have brought the officers into close range with a still armed man.

A firearm would have defeated the purpose of attempting to assist Mr Caristo to stop further harming himself and the officers had not been in direct threat outside the home and therefore discharging a firearm was not justified, he said.

Other officers provided interviews corroborating Mr Caristo's actions and their belief the Taser had been the only suitable option.

Acting Sergeant Macklin discharged one cartridge from the Taser into Mr Caristo It subdued him and other officers were able to remove the knife and handcuff him.

"I remember thinking that everything was going to be alright now," Acting Sergeant Macklin recalled.

Paramedics attended to Mr Caristo within a minute of him being handcuffed but he died at the scene.

Mr Archer referred to excerpts from Professor Johan Duflou's autopsy report, which concluded there had been no evidence of excessive force used on Mr Caristo.

The autopsy found very high levels of methamphetamine in Mr Caristo's blood and moderately advanced heart disease.

The report stated that in the absence of other features, Professor Duflou would be willing to state the cause of death as a drug overdose.

However, Mr Archer said when called to the stand he expected Professor Duflou to say the cause of death was cardiac arrest after using methamphetamine and being subjected to the electric shock of the Taser.

The inquest continues.