It is "entirely possible" the same weapon was used to stab two cousins during a deadly brawl at a Canberra skatepark, an expert has told the jury in a murder trial.
Professor Johan Duflou made that observation on Tuesday in the ACT Supreme Court, where a 17-year-old boy is standing trial.
The boy has pleaded not guilty to a charge that he murdered an 18-year-old man, who was stabbed up to six times during a fight at the Weston Creek skatepark in September 2020.
He has, however, pleaded guilty to a charge of recklessly inflicting grievous bodily harm on the deceased's 16-year-old cousin, who survived what Professor Duflou described as a "gaping" wound to the lower back.
Neither the cousins nor the alleged killer, who was 15 at the time of the incident, can be named for legal reasons.
Professor Duflou, an experienced forensic pathologist, conducted an autopsy on the 18-year-old victim and considered medical records relating to the 16-year-old.
On Tuesday, he took the jury through his findings and opinions on the cousins' various injuries.
Professor Duflou said the 18-year-old's body showed signs of six sharp force injuries, with five of these stab wounds and the other "somewhere between" a stab wound and an incised wound.
He concluded that rapid blood loss resulting from the injuries had been the young man's primary mechanism of death.
The forensic pathologist said he believed a knife with a blade at least 10 centimetres long was likely to have caused the deceased's injuries.
Asked whether the same weapon might have been used on the 16-year-old cousin, he said there was "a lot of uncertainty".
"But the answer in general is yes, it's entirely possible," Professor Duflou told the court.
The trial, before Chief Justice Lucy McCallum and a jury of 13, continues.
The jury has previously heard the fight, which involved 12 children and adults, occurred when three carloads of people converged on the skatepark as a result of an argument that had broken out over Snapchat.