Rogerson, 83, has always argued his innocence, claiming he was unaware of fellow crooked former detective Glen McNamara's plans to murder the 20-year-old.

Mr Gao was lured to a darkened storage shed in the city's south and shot dead before the former police officers attempted to cover their tracks by dumping his body at sea.

The sentencing judge said although gunshot residue found on Rogerson's clothing pointed to the possibility he was the triggerman, he couldn't be sure who fired the fatal shots.

Both hero and villain during a 28-year NSW Police career, Rogerson was at one time considered the force's most decorated officer.

The culmination of his recognition was to receive the coveted Peter Mitchell Award for outstanding police work in 1980 but within six years, his career had unravelled spectacularly.

In 1981 he was controversially found responsible for the fatal shooting of another young drug dealer, Warren Lanfranchi, but deemed to have acted in the line of duty.

However Lanfranchi's girlfriend, sex worker Sallie-Anne Huckstepp, soon after alleged Rogerson deliberately killed him over a drug-related dispute involving corrupt police. Huckstepp, herself, was later found drowned and her murder remains unsolved.

At the peak of Rogerson's demise, he was also implicated in the attempted execution of NSW undercover operative Michael Drury after the similarly decorated drug squad detective declined to accept a bribe in exchange for evidence tampering in a heroin trafficking trial.

Drury was shot twice through his kitchen window on Sydney's north shore. Rogerson was charged and eventually acquitted of the attack in 1989 but by then had already been drummed from the force for depositing $110,000 in bank accounts under a false name.

Richard Roxburgh portrayed Rogerson in the 1995 mini-series Blue Murder and its 2017 sequel Blue Murder: Killer Cop.

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