Investigators circling the executioners of Sydney gangland figure Raphael Joseph hope a $1 million reward will provide the final piece of evidence needed to arrest his killers.

More than four years after his murder the massive reward is designed to tempt members of the bloodthirsty underworld to turn on each other – or give a family member the right push.

Joseph, 37, was last seen getting into a silver Commodore at McDonald’s Auburn in March 2014.

Six years earlier he’d been extradited from the United States over his suspected role in a fatal shooting in 2002, which sparked a wave of violent recriminations across Sydney’s southwest.

The accused killer and drug lord spent his final years trying to stay one step ahead of rival gangs and people eager to collect what he claimed was a $100,000 bounty on his head.

NSW Police homicide squad commander Scott Cook, on Wednesday, said he’s confident Joseph was murdered by “close associates”, stuffed into a 44-gallon drum and loaded into a van on Sydney’s outskirts.

For several days in February, police combed a Putty Road property at Blaxlands Ridge, where Strikeforce Halfbeak believe his body may be buried.

Investigators have masses of evidence, including suspect vehicles, but never found Joseph’s final resting place.

“We don’t expect to find his remains,” Detective Superintendent Cook told reporters in Sydney while announcing the reward.

“Detectives know who carried out the killing. They know it was more than one person and they know it was for “financial gain.

“We’re very close to a prosecution,” he said, noting the reward is designed to get the crucial, final piece of information.

The $1 million reward is one of only four in NSW and is among the largest in the state’s history.

It is, however, the only one for a gangland criminal.

The homicide chief called it a “one-off”, noting the rewards are investigative strategies, not indications of a person’s value.

“These people are driven by greed. These people are driven by money and financial gain,” Det Supt Cook said.

“We cannot have people executed in NSW like this.

“We must do something about that and we’re very close. We just need a bit more assistance to get us there.”

He acknowledged those with the right information could be involved in criminal networks themselves and the money could end up in nefarious hands.

“If they are criminals and they’re active, chances are they’ll be arrested and charged with other offences anyway,” he said.

But for those who simply know and fear Joseph’s killers, Det Supt Cook says police will keep them safe and help them walk away with the fortune.

-AAP