Both men were on Wednesday convicted of Mr Gao’s murder following a four-month NSW Supreme Court trial in which they tried to pin the fatal shooting on each other.
Mr Gao’s family say the legal system has worked and found two dangerous criminals guilty.
“While this is the verdict our family were hoping would be delivered, true justice can never really be served,” they said in a statement.
During the trial much of what the jury heard focused on events at the Padstow Rent-A-Space shed in Sydney’s southwest on May 20, 2014.
CCTV footage from that Tuesday afternoon shows Mr Gao walking into the shed, but only Rogerson, McNamara and a silver surfboard bag emerging.
Wrapped in the board cover was the body of Mr Gao.
The former detectives had lured him to the darkened unit, where he was shot and had 2.78kg of methamphetamine taken from him.
Six days later, a fisherman spotted the body, wrapped in a blue tarpaulin and chains, floating off Cronulla Beach.
Rogerson, 75, and McNamara, 57, were in cahoots over the murder and plans to “rip off” the drugs, but turned on each other after being arrested.
Both spent several days in the witness box telling the jury the other had shot and killed Mr Gao.
McNamara told the panel of seven men and five women Rogerson pulled a pistol from his right pocket and shot Mr Gao after they bickered over money.
After killing Mr Gao the jury heard Rogerson then took aim at McNamara’s head.
“I’ll do you. Get up and help you weak c*** or you will be on the floor next to him,” McNamara said he was told by Rogerson, who also threatened to kill McNamara’s daughters.
Rogerson, however, told the court Mr Gao was already fatally injured and on the ground when he arrived at the storage unit.
Neither managed to convince the jury and after almost a week of deliberations it found both men guilty of murder and commercial drug supply charges.
McNamara blinked as the jury forewoman clearly announced the verdict: “Guilty”.
It is not the first time Rogerson has been on the wrong side of the law, and the disgraced former officer appeared to swallow after being told he too had been found guilty of murder.
McNamara’s daughter Jessica gave evidence during the trial and could be seen sobbing at the back of the courtroom.
Detective Inspector Russell Oxford praised his team.
“These two guys were Keystone Cops and they simply thought they could get away with this.
“I’m very proud of all that went into this … essentially we were looking for Jamie Gao and that drew us over to the Padstow area and then it was a matter of following the evidence,” he said outside court on Wednesday.
“It simply came down to the case of three men walking into a unit and two men coming out,” he said.
A sentencing hearing will take place on August 25, although McNamara has already indicated he will appeal against his conviction.