Experts in forensics and firearms say it's possible that a young man working on a Queensland crayfish farm was shot dead by another person.
The Brisbane Coroners Court on Tuesday heard it was also feasible that Jeffrey Lawrence Brooks accidentally shot himself in the chest on March 13, 1996.
A police investigation determined Mr Brooks died after trying to retrieve a shotgun from a utility vehicle and setting off the trigger in the process.
His parents, Wendy and Lawrie Brooks, never accepted that explanation and claimed he was killed by co-workers who saw the aquacultural scientist as threat to their jobs and stolen crayfish racket.
During the final day of evidence at the reopened inquest into Mr Brooks' death, NSW Police ballistics expert Lucas van de Walt testified that the 24-year-old was shot at close range at Beenleigh, south of Brisbane.
"The wound of the deceased was perfect on the edges. There was no sign of the (shotgun) pellets spreading," Mr Van de Walt said.
"That puts the muzzle of the firearm in real close proximity when fired."
Mr van de Walt said his job of reassessing the case's ballistic evidence was made harder by Queensland Police's decision to destroy the shotgun in the years after the original investigation.
Mr van de Walt said he found a similar Harrington & Richardson shotgun to the 1901-era model involved in Mr Brook's death and ran tests with the same barrel length and similar ammunition.
Another sign of a close range shot was that Mr Brooks' chest was struck and then penetrated by an expanding plastic 'wad' component of the shotgun shell.
"I am of the opinion that the muzzle of the shotgun was between 10 and 80 centimetres from Mr Brooks's left shoulder during the discharge of the firearm," Mr Van de Walt said.
During cross examination by the Brooks family's solicitor, Mr van de Walt said it was "possible" Mr Brooks was shot by someone else while he was sitting in the utility or kneeling on the ground due to his wound's downward angle.
Victorian Institute of Forensic Medicine pathologist David Ranson testified that he had seen a lot of firearm homicides and the victim was usually struck in the head, centre of the chest or abdomen.
"It's really very difficult to distinguish on the pathology points alone. (The shoulder) is not a primary target to kill somebody, however you have got to accept most shooting scenarios are dynamic with the victim moving," Dr Ranson said.
"I don't think on a purely pathological basis I could distinguish between homicide or accident - both remain possibilities."
Dr Ranson said it was "possible" someone stood above Mr Brooks and shot down at him and "feasible" that he could have accidentally shot himself while reaching through a vehicle window to grab the gun.
Coroner Donald MacKenzie said the inquest's findings, due in March, was going to be a "difficult exercise to put in writing".
"To the Brooks family, I hope that the last seven days have been of assistance to you in opening up the fissures of the unknown in this matter."
Speaking outside court, Lawrie Brooks said the expert forensic testimony "hadn't really cleared things up one way or the other".
Wendy Brooks said she still believed her son was murdered.
"We're hoping for a finding of homicide because we still believe in our heart and there has been nothing that has come up in the inquest that has changed our mind," she said.
