"It's 38-and-a-half and counting," his uncle Don Craigie told AAP.
Mr Craigie has spent each of those years fighting for answers after his 17-year-old nephew's body was found on the tracks outside Tamworth, in northern NSW, on the morning of January 16, 1988.
He hopes for new insights when Deputy State Coroner Harriet Grahame delivers her findings on Thursday, marking the end of a lengthy and complex inquest into Mark's death.
"We're hoping it can give us some kind of answers, but I don't know if it will give us any relief from our bloody angst," Mr Craigie said.
Mark's body was found on a rainy Saturday morning, near a crashed stolen Holden Torana.
An autopsy found the Gomeroi teenager died from a traumatic head injury.
The initial police investigation ruled he laid down on the tracks either deliberately or in a dazed state, something his family has never believed.
The family has long suspected foul play and believe the police investigation was hindered by racism.
During closing submissions in April, counsel assisting Chris McGorey said there were "substantial" deficiencies in the initial police work.
Those flaws included improper collection of evidence from the tracks, and the quick removal of Mark's body and the train.
Police also failed to involve detectives and did not immediately interview Mark's family or investigate any link between the teenager and the crashed car.
"(With) a more robust investigation ... the coroner and Mark's family would be far more likely in a position closer to the truth," Mr McGorey told the inquest.
It would be up to Judge Grahame to determine whether racial bias influenced the police's actions, he said.
Describing the investigation into his nephew's death at the inquest in 2025, Mr Craigie said: "That train would still be there if it was a white boy."
"They would have turned that train engine over."
The inquest also heard evidence Mark could not drive and would never steal a car.
That meant it was "highly likely" Mark was not alone when he ended up on the tracks, Mr McGorey said.
"These persons have not been forthcoming with what they know, or their identities have not been (revealed)."
Mr Craigie said the coroner's findings would likely be the start of a new chapter.
"There's the journey that I've been on and the realisation ... this journey may end, but also another one may begin, depending on the findings of the coroner," he said.
"I've always said it was because my nephew was a 17-year-old Aboriginal boy."
Judge Grahame will hand down her findings after a smoking ceremony at Tamworth courthouse.
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