A coroner has found that police inquiries into the death of a Palmerston father were tainted by "investigative bias" — an issue raised at other recent inquests in the Northern Territory.

Key points: The NT Coroner has delivered an open finding following a coronial inquest into the death of Matthew Rosewarne

The NT Coroner has delivered an open finding following a coronial inquest into the death of Matthew Rosewarne His death was investigated as a suicide

His death was investigated as a suicide The coroner says it should have been investigated by police as a potential homicide

Matthew Rosewarne was found shot in the back of the neck, with a gun beside him that had the safety catch on, in the shed of his Palmerston home on May 30, 2016.

Within an hour of arriving at the scene, authorities were convinced the 45-year-old had taken his own life.

But today NT coroner Greg Cavanagh said they should have considered it a possible murder.

"This death should have been investigated as a potential homicide. It was not," Mr Cavanagh said.

"The forensic team made a determination that it was a suicide within the first hour and did not seek to exclude the involvement of another person."

Today Mr Cavanagh delivered an open finding following a coronial inquest into Mr Rosewarne's death.

While he was unable to determine whether the death had been a suicide or a murder, he said the "the involvement of another person remains a real possibility".

But he said this possibility was difficult to probe further, given investigations that should have been made at the time were not.

Police failed to fingerprint, swab scene

During the inquest, the court heard at the time of his death Mr Rosewarne was drinking excessively, had told a mental health team he had hit "rock bottom" and had recently separated from his long-term partner, Christine Staines.

The Colt.45 was found near Matthew Rosewarne's body with the safety catch on. ( Supplied: NT Courts and Tribunals )

But he had denied suicidal ideation, thoughts of self-harm or harm to others.

It also heard his former partner Ms Staines was the last person to see him alive, two days before his body was found, when she took two handguns from his home, saying she was concerned for his welfare.

She was also the one who contacted police requesting they check up on Mr Rosewarne on May 30.

They found him dead at 2:30pm, with a gun beside him.

The safety catch was on, but the court heard they thought it must have slid on as the gun hit the ground.

Mr Cavanagh said authorities decided it was a suicide within the hour.

This meant that examiners failed to fingerprint or swab the scene, did not test for blood splatter, did not test open beer bottles for DNA and fingerprints and did not test the two handguns removed from the house by Ms Staines two days before, the inquest heard.

Mr Cavanagh said his office raised with police a number of times that there were issues with the level of assurance that the gunshot wound was self-inflicted.

"However those communications seemed only to strengthen police steadfastness that the death was due to suicide," he said.

Police 'explained away' red flags: Coroner

In handing down his findings today, Mr Cavanagh pointed to the role of "investigative bias" by police, adding this had been an issue in a number of recent inquests including that of Sasha Green.

He said there were at least two red flags — the safety catch being on and the bullet entering the back of his neck — but police explained them away.

"They seemed committed to the hypothesis that the death was self-inflicted and did not seek to exclude third party involvement during the forensic stages of the investigation," Mr Cavanagh said.

"Thereafter the case continued to be investigated as a suicide rather than a potential homicide."

However, he said police had since conceded this was inappropriate, and were taking steps to ensure it did not happen again.

He said there had been a thorough identification of the issues and a demonstrated willingness to learn and improve by police.

"This is the best response by Police I have received for a number of years," Mr Cavanagh said.

Involvement of another person a 'real possibility'

In handing down his findings, Mr Cavanagh also referenced a submission made to him on behalf of the Commissioner of Police, Reece Kershaw.

Matthew Rosewarne was found dead on May 30, 2016. ( Supplied: NT deputy coroner )

While the submission noted the failings in the police investigation, it said that suicide was "overwhelmingly probable", and there was "nothing in evidence that was inconsistent with suicide".

It urged against delivering an open finding, saying that may prevent Ms Rosewarne's family from reaching closure.

But Mr Cavanagh responded that if the only evidence was of suicide because that was all police investigated, "that evidence is somewhat less compelling".

While he agreed the open finding may leave Mr Rosewarne's family unable to reach closure, he said that could not be cured by a simple finding.

"The involvement of another person remains a real possibility. One that was ignored. I am now asked to similarly ignore it. I cannot," he said.

"It is plain that Mr Rosewarne died from a gunshot wound to the neck.

"However the circumstances of how that occurred remain open."

Today, NT Police Acting Assistant Commissioner (Crime and Darwin Metro) Travis Wurst said it accepted the outcome of the inquest and acknowledged the open finding in relation to the death of Mr Rosewarne.

He said police will consider the findings and "set our position in relation to that determination".