At a monthly criminal case management hearing in the West Australian Supreme Court on Wednesday, prosecutor Carmel Barbagallo revealed clothing had been obtained from a Telstra worker from the 1990s.

She said it was being analysed so fibres could be compared with others in evidence, but the report may not be ready until mid-to-late June.

"The potential of this evidence, we say, is quite significant," Ms Barbagallo said.

Asked whether the clothing was linked to Edwards, who worked for Telstra at the time, Ms Barbagallo said it was "utilised by technicians at that time".

But she said she had to be careful not to reveal too much to ensure she did not compromise what detectives were doing.

Edwards, 50, is charged with murdering Ciara Glennon, 27, Jane Rimmer, 23, and 18-year-old Sarah Spiers, who were all last seen in Claremont between 1996 and 1997.

He is also accused of attacking an 18-year-old woman at her Huntingdale home in 1988 and twice raping a 17-year-old girl at Karrakatta cemetery in 1995.

The nine-month trial, sitting without a jury, is scheduled to begin on July 22, but defence counsel Paul Yovich has foreshadowed that date is now unlikely.

He said his fibre expert would need about eight-to-12 weeks to review the final report.

Justice Stephen Hall has not changed the start date yet, but has flagged his concerns.

"This is going to potentially imperil the start of the trial," he said.

Ms Barbagallo said everyone working on the case was "acutely aware" of the urgency but did not want to make any errors.

She said police were continuing to pursue the case.

"The police are damned if they do and damned if they don't," she said.

Edwards is due back in court for a two-day hearing starting on June 18.

Outside court, Ms Spiers' father Don was asked if he was frustrated by the possible trial delay and said: "That's the process and that's to be accepted."

Australian Associated Press