The long-running and hugely expensive investigation into the Claremont serial killings had a turning point after a DNA breakthrough more than a decade after the first murder, a detective has told a Perth court.
Bradley Robert Edwards, 51, is on trial in the WA Supreme Court accused of murdering Sarah Spiers, 18, Jane Rimmer, 23, and Ciara Glennon, 27, in 1996 and 1997.
The former Telstra technician admits raping a 17-year-old girl he abducted and dragged through Karrakatta cemetery in 1995 and attacking an 18-year-old woman as she slept in her Huntingdale home in 1988.
Former Macro Taskforce investigating officer Detective Sergeant Jim Stanbury testified on Monday about the DNA breakthrough at a UK lab in 2008 that linked Ms Glennon's murder to the 1995 rape.
Det Sgt Stanbury and former PathWest scientist Laurie Webb had delivered some exhibits,, including Ms Glennon's fingernails, to the UK lab for low copy number DNA testing.
"We saw that there had been no testing of that item (her left thumbnail) previously and considered it to be a good item for specialist forensic DNA testing," the detective said.
He said testing on a combined sample of Ms Glennon's left middle fingernail, known as AJM42, and her left thumbnail, known as AJM40, revealed a profile "consistent with DNA coming from two people - male and female".
The male profile was run through the UK's DNA database but returned no match.
It was later run through WA's database, which matched it to the unsolved cemetery rape case.
Det Sgt Stanbury said it was "definitely a turning point" for the investigation.
"Now that we had this match to the sex assault ... we had a living witness, we had a description of the person responsible, we had a vehicle ... that was possibly involved, we had a method (or) style of assault ... and of course we had the highly discriminating DNA profile," he said.
Det Sgt Stanbury said police no longer had to rely on alibis.
"We could target individuals for interview and for DNA and if their DNA didn't match, they would be eliminated from the investigation," he said.
Det Sgt Stanbury said he flew to New Zealand in 2009 to retrieve DNA extracts still in storage there following testing done in 2004.
More items were taken to the UK for testing and after the lab shut down a couple of years later, Det Sgt Stanbury arranged for about 500 exhibits to be returned to Perth.
"Everything was sealed and sealed again, perhaps in another bag, and then sealed in the crate," he said.
"Then we arranged for them to be couriered back to Perth."
Among the exhibits were items related to other high-profile murders, including that of Supreme Court registrar and mother-of-two Corryn Rayney in 2007 and 11-year-old Gerard Ross in 1997.
Under cross-examination, Det Sgt Stanbury was asked about obtaining witness statements from other officers, including one who had handled the rape victim's clothes.
Det Sgt Stanbury denied suggesting any content for her statement.
Defence counsel Paul Yovich will resume cross-examining the detective on Tuesday.
Australian Associated Press