Long before Ivan Milat left his mark on Australia's criminal history, another serial killer may have stalked Sydney's streets.

It began on a hot morning on Saturday, December 10, 1932 when the naked body of sex worker Iris Marriott, who also went by the name of May Miller, was found raped and brutally beaten in Queens Park under the flame-red flowers of a coral tree.

Established in 1888, Queens Park still boasts several striking coral trees. (Centennial Parklands)

Less than a week later another sex worker, Bessie O'Connor, was found barely breathing in a pool of her own blood, naked, within the Royal National Park in Sutherland. She too, had been raped and beaten. She initially survived the attack but died the next morning in hospital.

O'Connor's murder changed things. She came from a respected family from Redfern and the media was quick to jump on the story of a "crazed sex-attacker."

An article from the newspaper 'Truth'. O'Connor's murder got significantly more media attention than Marriott's. (Supplied)

Spurred by media and public pressure, the police quickly set their sights on a suspect - Eric Roland Craig – a man later sentenced to death for the murder of O'Connor.

A 'pattern' of vicious, public murders

Tanya Bretherton is the author of 'The Killing Streets', a book which details the cases.

She believes the murders could possibly be the work of a serial killer.

Through her research she discovered a third woman, Hilda White, also a sex worker, had been murdered in July, 1932.

Like the others, White's body was found naked, beaten, and raped under a fig tree in Centennial Park in Sydney's east.

White's murder was the first in a spate of killings in 1932, Miller's occurred in December. (Supplied)

"It was the cluster of cases in 1932 that really had me first going backwards and then forwards to see if there was a pattern," she told 9News.com.au

"It was when I saw Bessie was the third that year, I thought 'there's something not right here.'

After more digging, Bretherton noticed more cases that fit the pattern; scores of murdered women found beaten, naked and raped spanning back to 1922, and past 1932 to 1946.

A timeline and location of each murder, Bretherton believes could be related. (Nine)

"It's 10 women over the course of a 25-year period that I uncovered," Bretherton said.

"Because the majority were all found in the eastern suburbs, and from what we know, most, with some exceptions, were working as prostitutes in a similar area of Sydney, I think they were related."

An innocent man

Bretherton believes Eric Roland Craig was innocent.

She said he was convicted on scant evidence and detectives in 1933 used controversial interview tactics to coerce a confession.

Eric Roland Craig confessed but later maintained his innocence. (Supplied)

"Everything we know now about how it is possible to extract a false confession from someone was there on the night when they got the confession out of Craig," she said.

"He was under duress, he had been held for a long period of time, and the police lied openly about how much evidence was against him."

After enduring three trials, Craig received a manslaughter conviction for Marriott's death and was sentenced to death penalty for the murder of Bessie O'Connor, however this was commuted to a life sentence.

He was eventually released from prison and went on to have another life – changing his name, building a house in Merrylands and re-marrying.

A suspect in the wind

Bretherton said there is no way an alternative suspect can be found because most of the murder cases weren't properly investigated at the time.

Sydney Police Detective Sergeant Thomas McRae (centre) walks down a street with three police officials, Sydney, 20 March 1933. McRae was one of the lead detectives on the cases. (Trove / Fairfax archive)

This was because the women were all sex workers.

"I was shocked more had not been done to investigate what were really horrible and public crimes," she said.

"It was just not a high priority for the police because the women were prostitutes."

"Values of the time being as they were at what the women did as work was viewed very dimly.

"I know it was a different era, with limited forensics, but even understanding all of that, the level of judgement brought to bear on these women was very real."

More disturbing than the prospect of an unidentified serial killer, is the prospect the murders could be the work of multiple killers, Bretherton said.

Sydney Harbour Bridge, Sydney, 16 January 1933. No matter the point of history, Bretherton believes more than one person could be capable of the crimes. (Trove/ Fairfax archive )

"What's more frightening about this is that at any point in Sydney's history there's clearly more than one person capable of doing this.

"It's possible that over the course of 25 years it could have been more than one guy."