An IRA unit which conducted a secret investigation into the murder of a German backpacker could hold vital clues about her killer.
No one has ever been convicted over the death of Munich teenager Inga Maria Hauser in 1988.
However, republican paramilitaries considered passing information about the alleged murderer to the RUC (Royal Ulster Constabulary)at the height of the Troubles.
“They had identified somebody that was responsible from the Loughgiel area and we believe they had a debate amongst themselves about whether that information should be passed in one way or another to the police,” a source said.
Ms Hauser’s death remains among the most high- profile unsolved murder cases in Northern Ireland.
The 18-year-old’s body was found dumped in a remote part of Ballypatrick Forest outside Ballycastle, Co Antrim, 14 days after she was last seen alive on a ferry from Scotland.
Detectives believe a number of people may have been involved either directly or in the cover-up, and have previously said they only need fractional pieces of evidence to bring the chief suspects to justice.
A man in the rural area east of Ballymoney, Co Antrim, was seen soon after the murder with scratches on his face, sparking concern in the community that he was involved.
It is understood at least one of those involved in the IRA’s clandestine investigation may be dead.
However, the source added: “There may well be other people who were privileged to the debate that was held.
“We are now 30 years down the line. A lot of things have changed. A lot of water has gone under the bridge.
“These people may still have that knowledge. That debate indicates that they wanted this resolved.
“The fact that they were debating it in 1988 highlights that they thought this was something different.”
Police have a male DNA profile from the crime scene, but have yet to secure a positive match.
A number of years ago, in one of the largest DNA screenings ever undertaken in the UK, 2,000 samples failed to produce a definitive match to a male genetic profile found at the murder scene. However, officers have recently conducted further testing including a trawl of updated familial DNA samples.
Detective Chief Superintendent Raymond Murray, the officer leading the murder hunt, said: “We have been aware of this account of events for some time and I would reiterate my appeal for anyone with information to come forward. It is not too late to tell us what you know.”
Prior to her death, Ms Hauser travelled through England and Scotland and according to diary entries intended to travel south to Dublin when she docked at Larne, Co Antrim.
However, for reasons as yet unexplained, she ended up going in the opposite direction, to meet her death.
Mr Murray said: “Inga Maria’s family deserve to know what happened, deserve closure after 30 years.
“Her father died not knowing who killed his daughter and her mother has been ill for many years. The family have been tortured by her murder and we have been in close contact with Inga’s heartbroken sister in the run-up to this anniversary. Do the decent thing for Inga’s sister and mother.
“Think of the fear and pain she felt, think of her family not having justice.
“After 30 years, it’s time to tell us what you know.”