"I still believe the Provisional IRA murdered Gareth," his father Mark O'Connor insisted. Al-though police and the O'Connor family believe mainstream republicans were behind the murder, the dissident Real IRA has also come under suspicion.
But Mr O'Connor added: "I know this [that the IRA murdered his son] because they threatened Gareth and they threatened me."
Almost three years after the 24-year-old vanished while on route to Dundalk Garda Station, mystery still surrounds the case, coupled with ever-emerging conspiracy theories.
It had been feared the father-of-two, like many other such victims before him, had been 'disappeared' forever.
However, last June police received a tip-off from a priest, the full nature of which has never been disclosed. It led them to a section of Newry Canal, close to Victoria Lock, off the Omeath Road.
They recovered a submerged blue Volkswagen Golf the car Mr O'Connor was last seen driving through the south Armagh border village of Newtownhamilton on May 11 2003.
Inside lay his badly decomposed body.
Mr O'Connor was travelling to Dundalk Garda Station where he regularly reported as part of bail conditions imposed after he was charged in the Republic with membership of the Real IRA when he disappeared.
The timing of the recovery of his body, just over two years after he vanished, was not lost on some observers.
But the victim's father strongly rejected suggestions at the time that the development was part of a wider sequence ahead of an IRA statement on its future.
Despite the various 'why now' theories dominating reports and intense curiosity over the information supplied to the Church source that led police to the canal, his parents Bernie and Mark O'Connor had more pressing matters.
They had a funeral to organise, the Christian burial denied to Gareth for so long.
They were also optimistic hopeful they might now find out how and exactly why their son was murdered, and that any forensics gleaned through advanced technology may aid the hunt for the killers.
Police arrested what they described as "well-known" republicans in the days after Mr O'Connor's disappearance but they were released without charge.
Such was the state of the body DNA tests and dental records were needed to provide the official confirmation that it was that of Mr O'Connor.
An initial examination failed to establish the cause of death and further tests were needed.
These are now complete and the O'Connors have been dealt yet another blow outside a confession or any further advances in technology that could shed any more light, they may never know how their son was killed.
Police initially confirmed there were no outward signs of wounds, not surprising given the scale of decomposition.
But further analysis of the remains has left the O'Connors with many more questions.
The Irish News can today reveal that the autopsy results, which included bone marrow tests, concluded the cause of death cannot be ascertained.
An X-ray showed up no metal fragments that would have pointed to Mr O'Connor being shot.
There was no "unequivocal" evidence of drowning, no evidence of disease and no traces of any drug found.
With shooting ruled out, were there any signs of torture or other traces of injury?
There was nothing to suggest he had been tied up but due to the state of the body the possibility he was beaten cannot be ruled out.
However, there were no fractures to the skull or other bones, nor damage to the brain and internal organs of the chest or abdomen.
Due to the extent of decay, it is believed Mr O'Connor met his death shortly after he disappeared.
Forensic experts say a body in water decomposes at a slower rate than on land but this is dependent on factors such as the content of the water and its temperature.
According to Gareth's family, everything he left with the day he went missing was found in his car, including two mobile phones and money in the pockets of his trousers.
It is still unclear exactly how long the car was in the canal.
"At least if we knew how he died..." Mrs O'Connor said.
"Now we are in limbo. Everything is going through our heads. It is a complete mystery. Something happened to him, somebody knows something."
The O'Connors are still studying the report but have sought the advice of their solicitor over an accompanying letter from Coroner John Leckey.
"Mr Leckey said he doesn't feel it necessary to have an inquest but wanted to hear the views of the family before issuing a death certificate," Mrs O'Connor said.
"The police are still treating it as murder why no inquest?"
The O'Connors have rejected the IRA's denials of responsibility.
"I gave those names [of the killers] to Gerry Kelly [Sinn Féin assembly member]. But nothing has been done," Mr O'Connor said.
"Gerry Adams ignores us and ignores all the families of the Disappeared."
Last night (Thursday) a Sinn Féin spokesman said: "The IRA have made it clear that they were not involved in the disappearance of Gareth O'Connor. We accept totally this statement.
"It is our belief that the family should look towards either the republican micro organisation Gareth O'Connor was suspected to be involved with or the Special Branch he was alleged to be working for to further their search for justice."
The spokesman insisted Mr Adams continues to work to help to find the remaining Disappeared victims.
"Gerry Adams is deeply committed to this issue and to seeing this injustice ended," he said.
As well as how Gareth murdered, the question of why may have been buried with the victim.
Police have probed the possibility that the collapse of a 'pyramid' investment scheme, said to be fronted by an IRA man, as a possible motive.
But there is another theory one that has sealed the fate of other Disappeared victims who were abducted, killed and secretly buried by republicans in the 1970s and 1980s the claim that he was an informer.
The O'Connors have strongly denied this.
However, it is a claim unlikely to go away.
In 2004 Gareth O'Connor was named during the trial of four men later cleared of Real IRA membership.
It was alleged in court that the murdered man was an informer who set up the accused.
Mr Justice Girvan said at the time: "The role of Gareth O'Connor remains enigmatic as an informer playing an active role in liaison with the police"
The O'Connors will leave such intrigue to others all they want to know is if their son suffered in his final hours.