The family of Sydney student Jamie Gao who was shot and killed by former NSW police detectives over a dodgy drug deal have released a statement after a jury handed down guilty verdicts for both men.

Roger Rogerson and Glen McNamara were found guilty of murdering the 20-year-old and found guilty of possessing a commercial drug supply after the jury accepted prosecution allegations that they "ripped off" Mr Gao of 2.78kg of the drug ice.

McNamara, 57, and Rogerson, 75, pleaded not guilty to the shooting murder of the 20-year-old Gao in a Padstow storage unit on May 20, 2014, before stealing 2.78kg of the drug ice from him and dumping his body at sea.

They blamed each other for the 2014 murder.

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Gao's family claimed "two very dangerous criminals have been found guilty" in a statement shortly after the verdict.

"Today the legal system worked," the statement read.

"But while this is the verdict our family were hoping would be delivered, true justice can never really be served. Yes, Jamie was a young man who had made some mistakes - but what young person hasn't?

"No 20-year-old deserves to lose their life over a stupid mistake. No matter what today's findings are or the sentence that is given, it won't change the fact that Jamie remains absent from the lives of our family - the people who love him - and we miss him every single day."

The southwest Sydney storage shed in which university student Jamie Gao was killed by Roger Rogerson and Glen McNamara. Photo / News Corp Australia
The southwest Sydney storage shed in which university student Jamie Gao was killed by Roger Rogerson and Glen McNamara. Photo / News Corp Australia
The floor of the storage shed where Jamie Gao was killed. Photo / News Corp Australia
The floor of the storage shed where Jamie Gao was killed. Photo / News Corp Australia

The trial of Rogerson and McNamara unfolded over four months at the NSW Supreme Court during which both men pointed the finger at each other over the shooting death of the young man.

Rogerson claimed he walked inside a Padstow storage unit on May 20, 2014, to see Mr Gao already dead on the floor.

But it took the jury of seven men and five women just under a week of deliberations to reject their version of events and find both accused men guilty of all counts.

Sitting composed in the court dock, Rogerson swallowed after the jury announced its decision on Wednesday while McNamara blinked when the verdicts were handed down.

Neither reacted when they were ordered to stand by Justice Geoffrey Bellew and formally convicted.

As the jury left Sydney's historic King Street courtroom after handing down its verdicts, only McNamara stood in observance with the age-old tradition.

Rogerson, wearing the over-size camel coat that had been his uniform throughout the marathon trial, slumped back in the oak-panelled dock.

In his closing address at the end of a three-month trial, crown prosecutor Chris Maxwell QC said both men were in on the scheme.

"This is a plan that would need two people - Glen McNamara to lure Jamie Gao down to unit 803 and Roger Rogerson to go down pretending to be the money man," Mr Maxwell told the Supreme Court on Thursday.

"The Crown says this is a two-man job, not just in achieving the rip-off but, equally importantly, in getting rid of the body, you might think, almost inevitably involving having two men."

McNamara has claimed he was meeting Mr Gao in the Padstow Rent A Space storage unit, where the murder is alleged to have occurred, to get information for a book he was writing about the triads.

Rogerson was to act as a second set of eyes, looking out for "suspicious cars with Chinese on board".

Prosecutors alleged the ex-detectives plotted to kill the student and steal 2.78kg of methamphetamine from him.

Key evidence at the trial was CCTV footage that showed Mr Gao enter the shed with McNamara, followed several minutes later by Rogerson.

The footage showed that about half an hour later the ex-detectives removed a surfboard bag which the jury was told contained Mr Gao's body.

The body was still in the surfboard bag and wrapped in a tarpaulin when it was found in water off Cronulla six days later. At the trial both Rogerson and McNamara claimed innocence and blamed each other over Mr Gao's death.

McNamara testified that Rogerson shot Mr Gao after arguing over a drug deal.

But Rogerson insisted he wasn't present for the killing, and said McNamara told him Mr Gao shot himself during a struggle sparked by a carjack attempt.

A sentence hearing will take place on August 25.