It follows the opening of an inquest today to discover if the body is that of Noel McGlynn of Ballaghderg, Letterkenny.
Mr McGlynn, 26, went missing on June 17, 1983 and was never seen again.
Just nine days later, on June 26, a body was found on a beach in Dunfanaghy.
The body was buried in an unmarked grave at the local Holycross Graveyard.
Now the brother of the missing man believes it was his body which was washed up and buried in the unmarked grave.
Yesterday’s inquest heard from a number of witnesses connected with the case.
William Sheridan, a member of Sheephaven Sub Aqua Diving Club, recalled how he was alerted to a body which had been washed up near Horn Head on June 26th, 1983.
He revealed how a member of the public had alerted them when they were diving and they managed to remove the body from rocks before the tide washed it back to sea.
James McGlynn said he was convinced the body is that of his brother whom he last seen at the family home having tea and then tidying his room.
He recalled how his brother had been admitted to St.Conal’s Psychiatric Hospital in Letterkenny a short time earlier and was suffering from depression.
“I am not completely sure it is him but I am 90% sure it is him because of the timeframe,” he said.
Mr McGlynn was shown pictures of his late brother and of the unidentified body.
Pathologist David Barry revealed how he carried out a post mortem on the unidentified body the day after it was washed up.
He said there was no sign of a violent death but there was no way of identifying a cause of death.
He put the age of the body as between 40 and 50 years, of medium build and was balding.
Although this did not completely tally with Mr.McGynn’s appearance, Dr Barry said he could not rule out that it was not him.
Coroner John Cannon said he was reluctant to order an exhumation of the unidentified body.
However he said he was satisfied that tissue samples taken from the unidentified body could be matched with saliva samples taken from Jim McGlynn by Gardai and solve the mystery.
He adjourned the case until January 17th next.