The man had been evasive about how he had received the scratches, finally saying his dogs had jumped up on him.
Mr Silas said this week he believed the scratches had been made by a person, because each scratch was about5mm wide and they were spaced like human fingers.
He said he had called another supervisor, now aged 31, who sneaked a look at the scratches.
Mr Silas said the casual employee man had frequently claimed to be famous, and some days after Ms Glennon was found the man had said he was "more famous than Christopher Skase".
Mr Silas had become frustrated at what he saw as lack of police action, and turned detective himself. He'd made excuses to call at the former casual employee's home and to check out his van.
He said that once he had seen what appeared to be a pattern of blood spots on the inside roof of the van; they had gone brown after being treated with an organic cleaner.
The man had once unbolted the front seat of the van and said he was looking for an earring. His girlfriend did not wear earrings.
She began wearing a claddagh ring, but did not know what it was.
Ciara Glennon had been wearing a claddagh brooch when she disappeared. It has not been found.
Mr Silas and his workmates said the man had missed work the Monday after Ms Glennon's weekend disappearance.
He said detectives had not interviewed the man until eight months after Mr Silas' first call
The men, who say they represent a group called Citizens for the Apprehension of the Real Killer (CARK) called thepress conference because they say their suspicions had not been fully investigated by Police
Letters from the police show Mr Silas's information has been dealt with.