He found petrol inside the victim's organs as well of traces of soot, which he said suggested he was alive when set alight.
Upon cross-examination from Kumar's lawyer Ron Mansfield, he accepted there would have been similar findings had Mr Prasad been unconscious at the time the petrol was ignited.
"Mr Prasad may have lost consciousness... as a result of a head injury and that may have been accidental. It could've been from a fall, a motor vehicle accident or striking his head against on object, or through assault," Mr Mansfield suggested.
"They're possibilities, yes," said Dr Garavan.
The defence lawyer also raised the possibility of "positional asphyxia" where someone became unconscious their airways could be blocked due to the position of the head or tongue.
"Panicked by what occurred... someone might think they're dead," Mr Mansfield said.
Dr Garavan accepted that was possible.
The jury heard the fire was lit by the roadside and might have taken a minute to run along a petrol trail to Mr Prasad.
Dr Garavan said there was no evidence the victim had been bound by the wrists or ankles and said it was reasonable to say he would have fled if he knew the fire was approaching.
The trial before Justice Geoffrey Venning and a jury of six women and six men is scheduled to last another couple of weeks.
The Crown case is expected to conclude early next week.
