It is the murder mystery that has plagued Queensland Police for 36 years.

Now the family of missing hitchhiker Tony Jones believe they have found the crucial evidence that could solve the cold case and lead to criminal charges.

Perth man Tony Jones was last seen in Townsville on November 3, 1982. He had been backpacking around north Queensland.

He had phoned his family and told them he planned to hitchhike from Townsville to Mount Isa.

The 20-year-old then disappeared without a trace.

His brother Mark Jones has tirelessly followed every lead into his brother's case ever since.

Tony Jones disappeared without a trace. ( Supplied )

"We got information four or five years ago about possible suspects in this case," he said.

"We thought those suspects looked strong, it started to explain what might have happened to Tony. In recent weeks, we've been given information that has confirmed our suspicions.

"We now believe that he was picked up by a group of young people and taken to Hughenden. Events unfolded that ended up with Tony being killed and his body being disposed of on that evening."

Tony Jones' body has never been found, but a 2002 coronial inquest ruled he had been murdered.

Due to ongoing criticism of the investigation, the Attorney-General agreed to another inquest, which began in 2016.

It was adjourned when the family launched a Supreme Court bid for a third inquest, arguing the most recent inquiry was set up under old laws.

A spokesperson for the Queensland Coroner said the inquest had been adjourned until further notice, and that "under Queensland law, the coroner cannot deliver findings while a matter is subject to court action".

Queensland Police have said they are waiting for the findings of that second coronial inquest, while a $250,000 reward for information remains on offer.

But Mark Jones said the case was in limbo.

"These are compelling new leads and we believe that these could and should lead to criminal charges being laid," he said.

Mark Jones is still searching for his brother Tony Jones, who disappeared in 1982 ( ABC News: Marcus Alborn )

National Missing Persons Week launched by Jones family 30 years ago

This week marks the 30th anniversary of National Missing Persons Week (NMPW) which was set up by the Jones family so that Tony and others like him would never be forgotten.

Trish Halligan from the National Coordination Centre said these families suffer what is called an ambiguous loss, not knowing whether their loved ones are still alive.

"As human beings we love to know the why, the how," she said.

"When someone goes missing, families don't have these answers. It's very difficult for them to move forward with their lives."

Across the country, the Australian Federal Police are dealing with 2,600 ongoing missing persons cases.

Another 38,000 people are reported missing each year.

Mark Jones said while NMPW had come a long way in strengthening communication between police in different states, grieving families needed more support.

"[It] always just feels like it's never quite enough and whilst it helps people get publicity that they badly need, it doesn't always get the resolution that they need," he said.