An autopsy to be carried out today on the exhumed body of Mr Richie Barron will aim to establish if he died as a result of an assault or a hit-and-run accident.
When Mr Barron's body was found on a roadside near Raphoe, Co Donegal, in October 1996 with serious head injuries, it was assumed he died as a result of a hit-and-run. The State pathologist was not called, and the scene was not preserved.
Subsequently, a murder investigation was launched but doubt about the cause of death remains.
The pathologist who carried out the post-mortem examination was not a forensic pathologist but his report showed serious injuries to the skull and internal bleeding.
A part of Mr Barron's broken dentures was found deep in his throat.
The Garda handling of the investigation into Mr Barron's death led to allegations of corruption against members of the force and the biggest internal inquiry in Garda history.
His family, who firmly believe he was murdered, said yesterday they hoped the issue would be resolved after the autopsy by State pathologist Dr John Harbison.
Donegal Division Chief Supt Nacie Rice said yesterday: "We are at a point now where we must establish this." He said the investigation into Mr Barron's death had been ongoing since the incident and that this had been running separately from the investigation by Assistant Commissioner Mr Kevin Carty into allegations of corruption against members of the force.
Chief Supt Rice said the team investigating the death, made up of officers from the Donegal division and the northern region, had decided the body should be exhumed. The daughter of Mr Barron, Ms Deirdre McGlinchey, told The Irish Times last month that the family were informed by members of the Carty team two years ago that the body was to be exhumed within two weeks. They never heard anything more about it until now.
Chief Supt Rice said he couldn't say why the family had been told this two years ago or what "was in people's minds then". He could not say why the exhumation had not happened before now.
Ms McGlinchey said yesterday it was very upsetting for the family, but they hoped it would help resolve some of the issues.
"We just hope it will get a definite cause of death. It is hard to take in - it is an awful thing to have to do. But hopefully it will draw a line under some of the things anyway," Ms McGlinchey said.
Meanwhile, Chief Supt Rice confirmed that an internal disciplinary inquiry, separate from the Carty investigation, was continuing at Letterkenny Garda Station.
This disciplinary inquiry started in April under Chief Supt Ray McAndrew from Cork, who brought a team of officers with him.
Chief Supt Rice said four members of the force have had notices served on them that they were being investigated as part of Chief Supt McAndrew's inquiry.