Accused Claremont serial killer Bradley Robert Edwards has pleaded guilty to five of eight charges, including twice raping a 17-year-old girl, but maintains he didn't commit any murders.
The 50-year-old denies the accusations he killed Sarah Spiers, 18, Jane Rimmer, 23, and Ciara Glennon, 27, who were all last seen on the affluent Perth suburb's entertainment strip in 1996 and 1997.
But Edwards has admitted breaking into a Huntingdale home in 1988 and attacking an 18-year-old woman as she slept and to raping the 17-year-old at Karrakatta cemetery in 1995.
At a Supreme Court of WA directions hearing on Monday before next month's judge-alone trial, Edwards changed his pleas from not guilty to guilty to aggravated burglary, two charges of deprivation of liberty and two of sexual penetration without consent.
His trial, previously expected to last nine months, is now expected to be at least three months shorter.
The court previously heard Edwards' DNA was found on a silk kimono left behind after a struggle at the Huntingdale house, on the cemetery rape victim and under Ms Glennon's fingernails.
Edwards was arrested and charged in December 2016 after DNA on the kimono was re-tested.
Prosecutor Carmel Barbagallo said on Monday it appeared the defence team would argue the physical evidence had been contaminated.
Edwards' lead lawyer Paul Yovich confirmed previous plans not to call DNA evidence may be revisited.
Fibre analysis will also be a significant part of the trial.
Ms Barbagallo, who argues the seriousness of Edwards' offending escalated over time, told a previous hearing the sexually-motivated Huntingdale attack involved entering the house through an unlocked door, pulling out telephone lines and closing the door to the victim's parents' bedroom.
Edwards then pounced on top of the vulnerable woman and tried to force a piece of fabric into her mouth but she fought back, and he also dropped a pair of stockings as he fled.
The cemetery rape victim was grabbed from behind, pushed to the ground, had her hands bound with a cord and fabric forced into her mouth.
In between these two offences in 1990, Edwards was convicted of assault for attacking a social worker from behind at Hollywood Hospital, where he was working for Telstra.
He tried to shove a piece of fabric into her mouth as he dragged her into nearby toilets, and cable ties were later found in his pocket.
A large focus of the hearing on Monday was the prosecution's "emotional upset" theory, that the murders coincided with key moments in the breakdown of Edwards' first marriage, which unravelled after he became distant and his wife had an affair.
These included the sale of the matrimonial home just days before Ms Glennon went missing, Ms Barbagallo said, but Mr Yovich argued the transaction would have been a relief, helping his client to move on.
Trying to asses the impact of emotional turmoil on Edwards was "a matter of guesswork", Mr Yovich said.
The remains of Ms Glennon, a lawyer, and Ms Rimmer, a child care worker, were discovered in bushland at opposite ends of Perth weeks after their murders, both with some form of neck injury.
The body of Ms Spiers, a secretary, has never been found.