Fibres found on the body of murdered schoolboy Gerard Ross matched those found on the bodies of Claremont serial killings victims Jane Rimmer and Ciara Glennon, the trial of the man accused of the women's murders has been told.

Key points: Gerard went missing soon after the Claremont serial killings

Gerard went missing soon after the Claremont serial killings Fibre evidence in Bradley Edwards's trial links the two crimes

Fibre evidence in Bradley Edwards's trial links the two crimes But no one has ever been charged over Gerard's death

Gerard, 11, went missing from the holiday home his family was renting in Rockingham, south of Perth, in October 1997 — just months after Ms Glennon was killed — and his body was later discovered dumped in bushes.

His killer has never been found.

Bradley Robert Edwards, 51, is on trial in the WA Supreme Court for the murders of Ms Rimmer and Ms Glennon as well as Sarah Spiers, whose body has never been found.

The three women disappeared from Claremont between January 1996 and March 1997.

Evidence presented at the trial suggests that police at one stage considered the same person may have been responsible for the Claremont killings and Gerard's murder.

ChemCentre fibre expert Rees Powell told the court on Tuesday he compared fibres found on Gerard's body to those found on the bodies of Ms Rimmer and Ms Glennon, as well as fibres found on the clothing of a 17-year-old girl raped in Karrakatta Cemetery in 1995.

Edwards has admitted raping the teenager but denies the three wilful murder charges.

98 critical clothing fibres

Blue wool and green polyester fibres were found to be common to the bodies of the murdered women and the 11-year-old boy.

But investigators did not consider them relevant as they matched the blue overshoe covers used by police at crime scenes and the green mortuary sheets used by mortuary staff.

None of the fibres matched 98 critical fibres in the Claremont case that the prosecution says links the Telstra technician to the murders of Ms Rimmer and Ms Glennon.

These include fibres found in the hair of the two women and on Ms Glennon's shirt, which Mr Powell testified corresponded with fibres found in the Holden Commodore work vehicle Edwards drove at the time and Telstra trousers of a type worn by Edwards in the mid 1990s.

Fibres from Edwards's car have been linked to two of the Claremont victims. ( Supplied: WA Supreme Court )

A database of thousands of fibres

Defence counsel Paul Yovich SC began cross-examining Mr Powell on Tuesday and sought to highlight the vast numbers of fibres collected that did not match Edwards's car or clothing.

Thousands of fibres were recovered from the victims' bodies, as well as more than 1,000 fibres from the clothing of the teenage rape victim.

Bradley Edwards is accused of murdering three women abducted from Claremont. ( Facebook: KLAC )

In total, ChemCentre uploaded more than 10,500 fibres onto its database from the Claremont investigation, including the Karrakatta rape fibres.

"To our knowledge, the Macro [Claremont] investigation includes the largest collection of vehicle fibres of any criminal investigation in Australian history," Mr Powell wrote in a 2019 report on the fibres prepared for the trial.

Under questioning from Mr Yovich, Mr Powell conceded fibres could have been transferred onto Ms Glennon's jacket after it was thrown under a table onto the floor at the Continental Hotel in Claremont, where the young lawyer had been drinking with friends and work colleagues.

The Continental Hotel in Claremont where Ciara Glennon was last seen. ( Supplied: Supreme Court of WA )

Fibres could also have been transferred onto the jacket after one of Ms Glenon's friends retrieved it from the floor and wore it around his waist briefly before returning it to her, Mr Powell said.

But under re-examination from prosecutor Carmel Barbagallo SC, Mr Powell said if this was the case critical blue polyester fibres found on Ms Glennon would have to match fibres found at the hotel, which had not happened.

Instead, the fibres matched trousers manufactured specifically for Telstra in the mid 1990s that Edwards would have been wearing during the period, Mr Powell told the court earlier.

A comparison of blue fibres found on Jane Rimmer's hair and Ciara Glennon's hair. ( Supplied: WA Supreme Court )

Ms Glennon's jacket has never been found, although witnesses have told the trial she was either wearing it or had it tied around her waist when she went missing.

Mr Powell finished his testimony on Tuesday afternoon after nine days, the longest of any witness to date.

Today the court will be sitting late to hear evidence from the prosecution's fibre expert, Dr Ray Palmer, who is scheduled to testify from the UK via videolink.