Bradley Evennett died with facial fractures, a brain bleed and displaced teeth after a violent backyard sparring session with a professional cage fighter.
Those injuries and the associated blunt force trauma were found in an autopsy to be the cause of his death on March 22, 2024.
The report found the 32-year-old's genetic disorder osteogenesis imperfecta type 1, also known as brittle bone disease, did not contribute to his demise.
At the NSW Supreme Court murder trial of Mr Evennett's sparring partner Bradley Dusan Fletcher on Thursday, clinical geneticist Andreas Zankl seemed to agree.
He told jurors the number and severity of the injuries were unlike any accidental injuries experienced by patients he had observed during his 25-year career.
"I've never seen an orbital or skull fracture that just happened by accident," he said under questioning by crown prosecutor Kate Ratcliffe.
"I’ve never heard of teeth being dislodged accidentally."
Professor Zankl said similar fractures could occur in those with brittle bone disease, but they required a degree of force.
"It’s not something that happens in daily life in all the cases I've observed," he told the jury.
Fletcher, now 39, has pleaded not guilty to murder after telling police his friend had died in a sparring accident.
The trained mixed martial artist has admitted his role in the death by pleading guilty to manslaughter.
This lesser plea has been rejected by prosecutors.
The two friends had moved into a sharehouse in the northwestern Sydney suburb of Melonba on the day the lethal sparring match took place.
They had drunk alcohol and taken cocaine before donning boxing gloves.
After Mr Evennett was lying face down in the backyard that afternoon, Fletcher did not call triple zero.
Instead, he dragged the dead man's body to a car, loaded it in the boot and drove to a nearby street before dumping it on the footpath.
Fletcher's then-girlfriend Jasmine Robinson was also due to move into the home with the two men.
She was at the house when the pair began sparring but left before Mr Evennett was killed.
She is expected to testify on Monday when the trial resumes.
