There has been a dramatic development in the Claremont serial killer case with accused murderer Bradley Edwards pleading guilty to attacks on two women, including the rape of a teenage girl.

Key points: Bradley Edwards is accused of murdering three women in Claremont in the 1990s

Bradley Edwards is accused of murdering three women in Claremont in the 1990s He was accused of two other attacks, including raping a teen girl in a cemetery

He was accused of two other attacks, including raping a teen girl in a cemetery He has admitted the two attacks, but continues to plead not guilty to the murders

The incidents include an attack on a woman in the Perth suburb of Huntingdale in 1988 and a rape of a teenager at Karrakatta Cemetery in 1995.

In a barely audible voice, Edwards pleaded guilty to the five charges — including sexual assault, deprivation of liberty and unlawful detention — as they were read out in the Supreme Court.

Earlier hearings were told Edwards broke into the home of an 18-year-old Huntingdale woman while she was asleep in her bedroom.

Her parents were home at the time, but were also asleep.

The court heard Edwards straddled the woman as she lay on her stomach and tried to force a piece of fabric into her mouth, but she fought him off and he fled.

However, a distinctive silk dressing gown was left behind and that garment could play a crucial part in the trial.

Previous hearings were also told details about the Karrakatta attack, in which Edwards grabbed a 17-year-old girl from behind, pushed her to the ground and used a cord with a "pre-prepared, improvised handcuff knot" to bind her hands.

He also placed a hood over her head and bound her feet together, before carrying her to his car and driving to the cemetery.

The teenager had been walking alone through Rowe Park after a night out in Claremont when the attack happened.

The trial of accused Claremont serial killer Bradley Robert Edwards is expected to last for months. ( Supplied: Central Crocs Football Club )

Edwards has a previous conviction for attacking a woman in 1990, in what has been labelled "the Hollywood Hospital" evidence.

The court heard he was working at the hospital as a Telstra technician when he attacked a social worker as she sat in a chair.

He tried to put a piece of material in her mouth, but she kicked him and managed to break free. Cable ties were later found in his pocket.

Edwards was convicted of common assault and sentenced to two years' probation.

Edwards continues to fight murder charges

Monday morning's pre-trial hearing opened with the change of pleas by Edwards, who is also charged with murdering Sarah Spiers, Jane Rimmer and Ciara Glennon.

The three women all disappeared from the upmarket entertainment district of Claremont between January 1996 and March 1997.

Bradley Edwards admitted two charges of attacking women in Perth in the 1980s and 1990s. ( ABC News: Anne Barnetson )

The bodies of Ms Rimmer and Ms Glennon were found in bushland, but Ms Spiers has never been found.

Edwards has continued to plead not guilty in relation to the three murder charges.

State prosecutor Carmel Barbagallo said the prosecution would be relying on fibre evidence common to the Karrakatta rape victim and both Ms Rimmer and Ms Glennon.

She said she anticipated the defence would try to argue a number of crucial items of forensic evidence, including samples taken from the bodies of the two women, had been contaminated.

But the prosecution had procured multiple witnesses, including forensic scientists and technicians, to testify that the samples had been treated appropriately were not contaminated.

Murders coincided with periods of 'emotional turmoil'

Monday's hearing was held to narrow down which evidence could be admitted at trial, including the prosecution's case that emotional turmoil in Edwards's life was linked to the killings.

Ms Barbagallo said the period between 1994 and 1997 was a time of significant emotional upset and instability for Edwards.

Bradley Robert Edwards is also accused of murdering Sarah Spiers, Jane Rimmer and Ciara Glennon. ( Facebook )

She said the relationship with his first wife was breaking down in late 1994 and early 1995, due partly to her infidelity.

This was around the time the Karrakatta Cemetery attack took place.

Ms Barbagallo said on Australia Day in 1996, Edwards turned up without warning at his parents-in-law's house in the southern suburb of Golden Bay. His estranged wife had been staying there after moving out of the marital home some weeks before.

He asked her to attend a fireworks display with him but she refused, which Ms Barbagallo contended left him upset.

That night Sarah Spiers disappeared from Claremont.

Jane Rimmer, Sarah Spiers, and Ciara Glennon all went missing from the Claremont entertainment district. ( ABC News )

At the time Jane Rimmer disappeared, Edwards had recently learned of his ex-wife's pregnancy to another man.

Ciara Glennon's disappearance was around the time Edwards and his ex-wife were signing documents to sell their house, Ms Barbagallo said.

Defence counsel Paul Yovich said there was no evidence Edwards had been emotionally disturbed during the time the murders were committed.

He said unlike the high-profile murder of Allison Baden Clay by her husband Gerard, where the motive was linked to the nature of the relationship between the murderer and his victim, "that's not the case here of course".

"The most that can be said is that over the course of the relevant period … there were times when the accused was happy or unhappy to an immeasurable degree," he said.

Mr Yovich said the emotional upset argument was entirely hypothetical and could not be proven.

Justice Hall reserved his decision on the emotional upset evidence.

Marathon trial may be cut short

Ms Barbagallo also said she expected the guilty pleas would cut short Edwards's trial by at least three months.

It was originally slated to last nine months.

Despite the development, Justice Stephen Hall indicated he would still like the trial to begin as scheduled on November 18.

Edwards will be sentenced for the Karrakatta and Huntingdale attacks at the conclusion of the trial.

Ms Barbagallo also raised the issue of Edwards's 2016 arrest, revealing that DNA had been collected from a Sprite bottle from which he had drunk prior to the dramatic police raid on his Kewdale home in December of that year.

This evidence had been "superseded by swabs taken while the accused was in custody".

Mr Yovich said he had no issue with the legality of the arrest and would not be contesting the evidence collected from the soft drink bottle.

Denis Glennon and Don Spiers have been a constant presence at court during Mr Edwards's appearances. ( ABC News: Hugh Sando )

A large crowd of police and members of the public was present in the public gallery in the Supreme Court in Perth to hear Edwards's admissions.

The onlookers included Ms Spiers's father, Don Spiers, and Ms Glennon's father, Denis Glennon, who have been a constant presence at each of Edwards's court appearances.

The hearing was delayed by more than 30 minutes because of a delay in getting Edwards to court.