Two British Home Office pathologists have given evidence to the tribunal regarding their examination of Raphoe cattle-dealer Mr Richie Barron following the exhumation of his body in 2002.
Dr Philip Lumb, a Home Office pathologist and lecturer in forensic pathology at the University of Sheffield, examined earlier reports. Mr Barron's skull showed two large fractures, one at the back of the head, the other at the front, he told the tribunal.
The pattern of fractures meant the rear injury occurred first. The front fracture stopped when it met the back fracture, forming a "T junction". He also found "scuff mark" scratches at the front of the head.
Dr Lumb said he divided injuries into mild, moderate and severe force. The two injuries to Mr Barron would require severe force, "the sort of thing we see in car accidents".
A broad, flat surface caused the injury to the back of the skull, he added. Mr Barron's neck rotated, causing an injury to his third vertebrae, and the front of his skull then came into contact with the ground "accelerated at great speed", explaining the cuts to the front of his skull and associated scuff marks.
The doctor could not identify what caused this acceleration, but it may have been a bumper or wing mirror. He said it was unlikely to be an assault.
"The pattern of injures fit quite well from being impacted by a vehicle," Dr Lumb said. "I have not seen an injury this severe as a result of an assault."
It was unlikely that Mr Barron's injuries were caused by being struck from behind, and then struck again by an object such as a brick as he fell forward, Dr Lumb told Ms Patricia Moran, lawyer for the Barron family.
"I've never seen a blunt heavy object such as a brick cause scuff marks. It's much more in keeping with an accelerated fall on to a heavy surface."
Dr Helen Whitwell, a professor of forensic pathology at the University of Sheffield, has worked as a consultant pathologist to the Home Office since 1998.
Only in murder cases where there had been multiple blows to the head had she ever seen a skull "literally smashed to pieces", as the back of Mr Barron's head had been. In such a case, several lacerations would be expected, but only one was found.
It was very difficult, if not impossible, to think of any combination of weapons that would account for the wounds Mr Barron sustained.
"It's not a scenario that I've seen or am happy with," the forensic expert said when asked if she had ever come across an injury like that to the back of Mr Barron's head as a result of a blow from a weapon. "Not from a weapon. In the context of road accident, yes."
There was nothing in the original autopsy report that would allow police to go to court, Dr Whitwell agreed. This was not a criticism of hospital pathologists as most have not had any forensic training. A suspicious death would trigger the involvement of a trained forensic pathologist.