Evidence of "graphic and extreme" pornography found on a computer seized from the home of alleged Claremont serial killer Bradley Edwards is not admissible at his trial, a judge has ruled.

Key points: Justice Stephen Hall says the pornography evidence is not relevant to the trial

Justice Stephen Hall says the pornography evidence is not relevant to the trial Evidence about a prior conviction and the "Telstra living witness project" will be allowed

Evidence about a prior conviction and the "Telstra living witness project" will be allowed About 580 witnesses are set to be called in the nine-month trial

Prosecutors had argued last month that the evidence, which included a pornographic movie and explicit stories about the rape and abduction of women, should be allowed at the trial, to show Mr Edwards had an interest in sexually attacking women.

However, in a complex judgement, Supreme Court Justice Stephen Hall has ruled the evidence — discovered on a computer at Mr Edwards's home almost 20 years after his alleged crimes — was not relevant.

He said there were several flaws in the state's argument that the pornography was relevant to the offences Mr Edwards was accused of committing.

"I do not accept that it can be assumed that the perpetrator of any of the offences was necessarily likely to have an interest in violent pornography," Justice Hall said.

"Nor [do I accept] that a person who had such an interest is more likely to have committed these offences."

The judge said it could not be firmly established when the pornography was possessed and created, other than between December 2015 and December 2016.

"Whilst it may be supposed that the activity of collecting and creating occurred over a period of years, it cannot be shown that any of that activity coincided with the commission of the offences, or was even close in time to those events," he said.

Sarah Spiers, Ciara Glennon and Jane Rimmer disappeared while out in Claremont. ( Fairfax Media )

Mr Edwards has pleaded not guilty to all charges, including the murders of Sarah Spiers, Jane Rimmer and Ciara Glennon, the three women who disappeared from the streets of Claremont between 1996 and 1997.

He is also accused of sexually motivated attacks on two other women, one inside a Huntingdale home in 1988 and another at a cemetery in Karrakatta in 1995.

'Common features' of attacks on women: judge

Justice Hall has allowed prosecutors to lead evidence about Mr Edwards's 1990 conviction for attacking a senior social worker at Hollywood Hospital, where he was working as a Telecom technician.

Bradley Edwards has pleaded not guilty to all charges and will face trial in July. ( ABC News )

"It is true that there are a number of features of the Hollywood Hospital incident that are different to both the Huntingdale and the Karrakatta incidents," he told the court.

"Those differences are relevant but, in my view, they do not detract from the underlying common features.

"Attacking an unknown woman from behind and using a piece of material or cloth in an attempt to prevent resistance are sufficiently similar to give this evidence significant probative value."

Evidence called the "Telstra living witness project" will also be allowed at the July trial.

This evidence details about five instances between 1995 and 1997 when a man, who was either driving a Telecom car or said he worked for Telecom, stopped and stared at young women or offered them lifts in the Claremont and Cottesloe areas.

Defence bid for separate Huntingdale trial rejected

Ruled out of the murder case against Mr Edwards was what prosecutors called the "Huntingdale prowler series".

The evidence relates to allegations he stole items of women's underwear off clotheslines and broke into or attempted to break into houses to commit sexually motivated crimes.

Justice Stephen Hall will handle the judge-only trial after ruling on evidence admissibility. ( Supplied )

But Justice Hall ruled that evidence could only be used by the prosecution as part of the case against Mr Edwards for the alleged Huntingdale attack.

He also rejected an application by the defence for the charges relating to that alleged attack to be the subject of a separate trial, unrelated to the three murder charges Mr Edwards is facing.

During Wednesday's hearing, it was also revealed about 580 witnesses are set to be called in the nine-month trial, although both the prosecution and defence lawyers said they would work to try to reduce that number.

Prosecutor Carmel Barbagallo said the trial would start with what she termed "the Edwards brief", dealing with his background, before proceeding chronologically.

Mr Edwards, who appeared via video link from Casuarina prison, was remanded in custody after the hearing until his next scheduled pre-trial hearing on April 24.