One of the men who raped and murdered Sydney beauty queen Anita Cobby has died in a Sydney prison overnight.

Michael Murphy, passed away from liver cancer in Long Bay Jail after being in palliative care for some months.

The 65-year-old was moved from Long Bay Jail, Sydney, suffering from advanced cancer in September last year.

Michael Murphy, one of the men guilty of killing Anita Cobby, was pronounced terminally ill in September last year. (Supplied)

A Corrective Services NSW spokeswoman confirmed to 9News Murphy had died at the prison hospital just before midnight last night.

“A 66-year-old man has died at Long Bay Hospital about 11.55pm,” the spokeswoman said.

“The Corrective Services Investigation Unit, which is part of the NSW Police Force, is investigating and will prepare a report on the death.

“All deaths in custody are subject to a coronial inquest, including deaths resulting from natural causes.”

Anita Cobby was raped and murdered in February 1986.

The nurse and former beauty queen had been having dinner with friends when she was snatched off the street and killed.

The 26-year-old had been set upon by five men while walking home from work in Blacktown in Sydney's west.

Anita Cobby was raped and murdered in 1986 by a group of men including Murphy. (Supplied)

She was savagely raped and beaten for hours.

One of her attackers slit her throat so badly she was almost decapitated.

Her body was found in a paddock not far from Blacktown.

Five men grabbed Anita Cobby off street and pulled her into a stolen car, and drove her to secluded a paddock where she was raped and murdered. (Supplied)

Twenty-six days after Ms Cobby died, John Travers, Michael Murdoch and three brothers - Michael, Gary and Les Murphy - were in custody.

Secret tapes used to catch the men confessing to the brutal murder led them being sentenced to life behind bars.

Anita Cobby was murdered in 1986. (AAP)

Anita Cobby posing for a photo with her younger sister Kathryn Szyszka when they were children. (AAP)

Following Murphy's death, Ms Cobby's sister, Kathryn Szyszka, told 9News she barely reacted to the news.

"If I'm to be honest, actually not a lot went through my mind," she said.

"I actually haven't given these criminals much time or thought over the years."

Police Minister Troy Grant, however, reacted to the news with more fervour.

"Regarding him - he can rot in hell," he said today.

One of Australia's most infamous murderers

A Current Affair crime editor Simon Bouda covered this case extensively and told Today why Murphy was considered one of Australia's most notorious killers.

“He and two of his brothers and two other men, John traverse and Michael Murdoch, murdered and slaughtered Anita Cobby who was a Blacktown nurse from Sydney's western suburbs back in 1986,” he said.

“It was one of the most brutal an horrific crimes we have seen.”

Anita Cobby's body was found in a paddock not far from Blacktown, west of Sydney. (AAP)

Bouda said Murphy was suffering from liver cancer and had been in and out of palliative care at Prince of Wales Hospital.

“We broke the story back last September that he was dying,” he said.