David, 21, went missing on May 22 last after escaping police custody in Co Tyrone and trying to swim across the River Foyle to his home in Donegal.
Despite a massive search involving the Gardai, PSNI and search and rescue teams, no sign of David has ever been found.
His family has always believed he drowned while trying to cross the river to freedom.
However his family now believe that clothing found close to Lifford Bridge belongs to the missing man.
The clothing was found by David’s brother Mark during a search of the banks of the River Foyle.
David’s father Joseph told Highland Radio’s Shaun Doherty that a tracksuit bottom and boxer shorts are unquestionably his son’s clothing.
“There was also red and white paint on the tracksuit bottom and David was painting his room just a couple of days before he went missing,” said Joseph.
The clothing has been sent away for analysis while a renewed search has now been planned.
“Now that we have the clothing then we can concentrate on a very specific area and hopefully find him.
“This is the breakthrough we have been waiting for and hopefully we can bring home David soon and give him a proper burial,” he said.Tags: