The morning after Mr Barron's body was found on the roadside, Sgt Niall Coady, a qualified scene-of-crime examiner, was sent there by Supt John Fitzpatrick, the inquest heard.
When Sgt Coady arrived, Mr Matt McBride and a member of his family were standing on the road with a yard brush and a bucket.
"I gather the road was cleaned before my arrival. There was a lot of water on one particular section and it had been swept," Sgt Coady said.
He cleared the people from the scene and carried out a forensic examination collecting flecks of paint, a particle of glass and strands of hair with follicles attached. These particles and Mr Barron's clothes together with an aluminium pipe and two sticks later found at the scene were forwarded to Garda HQ for forensic examination.
Department of Justice forensic scientists Dr Liam Fleury and Dr Martina McBride, who examined the clothes and other items, both provided reports to the inquest. Dr Fleury's report concluded that the glass particle was not recent and the paint flecks were different colours. His report stated that there was nothing on Mr Barron's clothing to indicate he had been knocked down by a motor vehicle but Dr Fleury added that she had seen hit-and-run cases where no evidence of the vehicle was found.
Dr McBride told the inquest that the aluminium pipe and two sticks found near the scene had no traces of blood and the only blood on Mr Barron's clothing was his own.
A toxicologist from Beaumont Hospital reported to the inquest that Mr Barron's blood alcohol level was 283 mg, more than three times the legal driving limit of 80 mg.
Det Sgt Sylvester Henry said he went to the morgue in Letterkenny General Hospital and viewed the body.
He said he noticed an injury to Mr Barron's wedding ring finger, and described it as having a jagged edge and there were injuries to the back of his hand.
"I was suspicious as to the cause of death and spoke to Supt Jim Gallagher.
"I could not see any physical signs of a hit-and-run such as paint or oil. I was not quite sure and felt it needed further investigation," Det Sgt Henry said.