Gunshot residue was found on Roger Rogerson's pants, shirt, pockets and hat just days after Sydney university student Jamie Gao was executed.
But there are three explanations as to how it could have got there.
The first possibility is that he fired a gun.
A second scenario is that he was in "close proximity to a gun at the time it was discharged".
And lastly he could have come into contact with an object or a surface that was contaminated with gunshot residue.
Regardless of how it got there, a gunshot residue expert has told the NSW Supreme Court that the clothing she tested "supports the proposition of a firearm association".
Mr Rogerson has denied shooting Mr Gao and is arguing his co-accused, Glen McNamara, pulled the trigger on the afternoon of May 20, 2014.
But Mr McNamara, a former policeman, says it was Mr Rogerson who shot the gun inside the southern Sydney storage shed.
Dr Stephanie Hales, who did her PhD on gunshot and explosive residue, told the court that there was no gunshot residue particles found on the two set of tracksuit pants seized from Mr McNamara.
"The absence of gunshot residue on the samples from the clothing of McNamara does not support or preclude the proposition of firearm association," she said in her report.
Despite the gun residue being found on four items of Mr Rogerson's clothes, Dr Hales could not definitively say whether he was the shooter.
"You cannot exclude the reasonable possibility that Rogerson was not the shooter and was not present in the storage shed at the time of the discharge of the firearm?" asked Mr Rogerson's barrister, George Thomas.
"That's correct," Dr Hales said.
In his opening address to the jury, Mr Thomas argued that Mr McNamara was the shooter.
Mr Rogerson opened a unit door at Padstow and saw Mr Gao "dead on the floor with a handgun lying near him".
"He says Mr McNamara appeared to be shocked and said a gun had been pointed at him by Jamie Gao and he was threatened," he said.
But Mr McNamara's barrister, Kara Shead, says her case rests on the fact that Mr Rogerson was responsible for shooting Mr Gao twice in the chest.
"He saw Mr Rogerson kill Jamie Gao in front of his own eyes and he was terrified," she said.
Both men have pleaded not guilty to murder and supplying a large commercial quantity of prohibited drugs.
Earlier on Thursday, Misaki Takebayashi gave evidence about how she desperately tried to call Mr Gao in the hours after he was allegedly killed and stuffed inside a silver surfboard bag.
Ms Takebayashi had been dating Mr Gao for about two months when she rang his phone and someone answered on the evening of May 20.
The person said "hello" in Chinese before hanging up on her.
She spoke of how Mr Gao had met Mr McNamara several times, including three days before his death at a pub in Hurstville.
"I recall times where I would be shopping in Hurstville with Jamie and he would receive a call on his mobile from Glen wanting to meet," she said in her police statement.
"Sometimes Jamie would be gone for hours."
The trial continues before Justice Geoffrey Bellew.
Read more: http://www.smh.com.au/national/gunshot-residue-on-roger-rogersons-clothing-20160224-gn2c6g.html#ixzz41WmFkeNi