A police detective has joined calls for a new inquest into the death of 17-year-old Aboriginal boy Mark Haines and said persons of interest have been identified, on the 35th anniversary of the young man's death.

On January 16, 1988, Mr Haines' body was found on train tracks 8 kilometres south of Tamworth in northern New South Wales.

Investigations in the years following have failed to deliver the resolution needed for a family and community still grieving.

In the lead up to the 35th anniversary of Mr Haines' death demands for action been renewed, calling out inadequacies from past investigations.

Legal representatives the National Justice Project said the family are expect a decision soon on whether the state's coroner will open a second inquest.

Gomeroi man, Uncle Don Craigie, has long fought for the truth behind the death of his nephew.

"After 35 years, there are still no answers," he said.

"With a fresh coronial inquiry and subsequent investigations by the Tamworth Local Command and the state homicide squad, we are hopeful that those investigations may shed light on exactly what happened to Mark."

Mr Craigie said he was convinced "foul play" occurred.

Mark's sister Lorna Haines is hopeful a new inquest in 2023 could bring some closure and also set a precedent for other families facing similar grief and uncertainty.

"It is still overwhelming and raw that no justice has come of it. My mother and father went to their graves not knowing anything about what happened to their son, which still leaves scars with myself and (my brother) Ro," Ms Haines said.

"Also, it may give the opportunity for justice for other Aboriginal families who have or are currently going through the same process as we are.

"I am hoping to finally get justice for our brother after the failings of the NSW Police in their attempt to do a half-hearted investigation.

"I am hoping for the people to be held accountable of the death of my brother."

Oxley Police District Detective Inspector Jason Darcy is supportive of a second inquest given the information at hand.

"Persons of interest have been identified in this case, but at this stage there's insufficient evidence to go to the next stage of a legal process," he told NITV.

"That's why a second inquest would be valuable. I do think a second inquest will hopefully give some answers to the family."

Detective Inspector Darcy did not comment on previous investigations.

It was reported the NSW Coroner received a review from the police and homicide squad into Mr Haines's file.

Representatives from the National Justice Project said a second inquest could shine new light on both the unknown circumstances of the death and the failings of earlier investigations.

"The NSW Coroner has the power to investigate not only the cause of Mr Haines's death, but to expose the inadequacies in NSW Police's investigations," solicitor Katrina Hawtrey said.

"The failure to adequately investigate Mr Haines's death was not just an isolated misstep by one police station – it was evidence of a systemic failure by NSW Police to handle Indigenous deaths the same way as non-Indigenous deaths."

On Monday NSW Greens MLC Sue Higginson continued her advocacy; calling for action and joining family members in front of Tamworth police station on the anniversary of the death.

"It is clear to all that the investigation into the circumstances of Mark's death was compromised and that there must be a new inquiry before more evidence or witnesses are lost to time and age," she said.

According to the ABC, fellow Greens MLC David Shoebridge is set to refer Mr Haines' death to the coroner, along with matters surrounding the deaths of three other Aboriginal men in NSW around the same period and in similar circumstances.