A coroner has admitted that Andrew Watt, whose family lives at Ettrickbridge, may have died after being chased in a French country lane.
Mr Watt, 31, from Durham, was found dead about a mile from Vimarce, near Laval, in north-west France, in September 2010.
Coroner Andrew Tweddle found that medication Mr Watt was taking could have been a factor in his death.
And he admitted that the family’s belief that he may have died after being chased was one of several possible scenarios.
However, he concluded that the cause of death could not be ascertained and recorded an open verdict at Crook Coroner’s Court last Wednesday.
French doctors had previously decided that the former Durham Johnston School pupil, who was taking medication for mental health issues, died of heart failure.
But Mr Watt’s family, which has waged a bitter five-year campaign to get to the truth of the circumstances surrounding his death, claims the inquest verdict means someone could have got away with murder.
Consultant pathologist Dr Paul Barrett, who conducted a post-mortem examination on Mr Watt’s body, told the inquest that a number of prescription drugs were found in his system.
And he said that the medication could have prompted a heart attack, but that he was unable to provide a cause of death with any certainty.
Detective Inspector Mick Bird, who examined the case, said that he believed the French police had conducted a “reasonable” investigation into Mr Watt’s death.
However, he conceded that he would have pursued more lines of investigation, including conducting house-to-house enquiries.
Mr Tweddle told Mr Watt’s family: “A possible explanation is that Andrew’s death may be linked to the medication that he was prescribed and taking.
“Possibly Andrew could have been chased at the time and that may have had an impact, but there equally may be other explanations.”
Mr Tweddle said there was no evidence to suggest Mr Watt had taken his own life or had been assaulted, adding: “The medical cause of death is unascertained. That inevitably draws me to only one conclusion and that is an open verdict.”
Mr Watt’s family, including mother and step-father, Julie and Les Sheppard, has repeatedly highlighted inconsistencies and gaps in the evidence provided by French authorities in a campaign that has seen protest marches outside the Foreign office in London and, at one stage, even saw the involvement of then French president Nicolas Sarkozy.
After the hearing, Mrs Sheppard commented: “An open verdict means they haven’t got enough evidence to make a decision, but they’re not prepared to ask the French for more evidence.
“(Someone in France) could have got away with manslaughter, murder or whatever.”
The coroner said he could reopen the case if significant new evidence was found.
But Mr Watt’s family, which has campaigned tirelessly alongside other families whose loved ones have died abroad in mysterious circumstances, said it would continue its own quest for answers.